THE PHYSICAL EDUCATION SERIES Edited by R. TAIT McKENZIE, BA., M.D., M.P.E. MAJOR, ROYAL ARMY MEDICAL CORPS PROFESSOR OF PHYSICAL EDUCATION AND PHYSICAL THERAPY, UNIVERSITY OF PENNSYLVANIA PHILADELPHIA ' ELEMENTARY ANATOMY AND PHYSIOLOGY/ A TEXT-BOOK FOR STUDENTS IN HYGIENE AND PHYSICAL EDUCATION BY MARY REES MULLINER, M.D. FORMERLY INSTRUCTOR IN THE SUMMER SCHOOL OF HARVARD UNIVERSITY; IN THE SARGENT SCHOOL FOR PHYSICAL EDUCATION; IN THE BOSTON SCHOOL OF PHYSICAL EDUCATION; AND IN THE DEPARTMENT OF HYGIENE, WELLESLEY COLLEGE; DIRECTOR OF THE AMERICAN SCHOOL FOR PHYSICAL EDUCATION ILLUSTRATED WITH 301 ENGRAVINGS IN BLACK AND COLORS LEA & FEBIGER PHILADELPHIA AND NEW YORK 1924 COPYRIGHT LEA & FEBIGER 1924 AUTHOR'S PREFACE. A teacher of the applied branches of a science, learns the fundamental preparation his students should have had by their reception and apparent understanding of the presentation of the more advanced subject. Having taught some of the applied phases of physical educa- tion, such as kinesiology, mechano-therapy and physical diagnosis, the writer has had opportunity of judging how complete a course in anatomy and physiology should precede the above subjects. Having planned such a course, the privilege of testing its sufficiency has not been lacking. Accordingly, the present book has been written from the above points of view. While it may fall short of realizing perfection, it is hoped that it may be found useful by other teachers. A knowledge of anatomy and physiology has a place in general education, especially as it may become a safeguard against the false information spread abroad by commercial parasites. It is, therefore, presented for consideration in high and preparatory school curricula, also. No claim is made for original research in the preparation of this book. It is frankly a compilation, and acknowledgment is hereby made of the use of the texts by Gray, Gerrish and Morris in anatomy, and of those of Foster, Howell and Jones and Bunce in physiology. M. R. M. Wellesley Hills, Mass. ;ih; EDITOR S PREFACE. Accurate knowledge of anatomy and physiology must always be the foundation on which physical training as well as the practice of medicine and surgery must rest. Of good text-books on general anatomy we have an abundant supply, but the publication of this work will fill a long-felt want in the field of physical education. Up to the present time students have had to use the large general text-books, which include a great deal of material not of direct use to them, if they are to get the main facts of anatomy and physiology so necessary for their training. No one could be better fitted to write such a text-book than Dr. Mary Rees Mulliner, both from her experience as a teacher and her training in physical education. Her career goes back to 1890, as a pupil of the normal class in physical education of the Boston Y. W. C. A. In 1891 she took advanced work and reading with Jakob Bolin on mechanotherapy, a course which she followed up by private lessons and postgraduate work with Baron Posse. She graduated, in 1896, from the Boston University School of Medicine and practiced until 1913, specializing in mechanotherapy. From 1902 to 1913 she lectured at the Harvard Summer School on mechanotherapy and during the same period at the Sargent School on anatomy and mechanotherapy. She also gave instruction in anatomy and physiology at the Boston School of Physical Education in 1913-1914. At the opening of the Ameri- can School of Physical Education, in 1914, anatomy was her subject. She was in charge of classes in war-reconstruction work under the Surgeon-General during 1918 and 1919, when she joined the depart- ment of hygiene at Wellesley College, in charge of corrective gymnastics. To such a one the lack of a text-book in anatomy and physiology for students in physical education has been apparent from the first and has become more and more acute as classes have increased. (v; vi EDITOR'S PREFACE For the present work she has had the advantage of using many of the splendid plates contained in Gerrish's American Text-book of Anatomy; plates that for clearness and perfection are unequalled. She has successfully avoided the condensation of the quiz-compends which fail from lack of the necessary illustrations and explanation. To students in physical education and to nurses a simple presenta- tion of the essential facts of physiology and anatomy must accom- pany a careful selection of the information that will have the most direct bearing on their own problems. This work does not com- pete with the large general anatomies in use for medical students. It will be a valuable handbook, however, to lay the foundation for the more detailed discussion of muscular action and the physiology of exercise which would naturally follow it in a well-regulated course on physical education. It thus takes its rightful place early in this series of books written for the use of students who wish to build soundly their knowledge of the body and its education. R. Tait McKenzie, Editor. CONTENTS. CHAPTER I. Introduction. Definitions 17 Names of Surface Parts 20 General Description of the Body 21 General Outlook on Relation of Parts of the Body ....... 21 The Framework 22 The Food Purveyors 22 The Carrier Organs 23 The Waste Removers 23 The Organs of Motion 23 The Master Organs 24 The Reproductive Organs 25 Properties of a Living Body 25 The Cell 26 Differentiation of Cells 27 Aggregation of Cells 28 The Intercellular Substance 28 Questions ■ 28 CHAPTER II. The Tissues of the Body. The Shape of the Cells 29 Connective Tissue 29 White Fibrous Tissue 30 Yellow Elastic Tissue 31 Areolar Tissue 31 Adipose Tissue 32 Gelatinous Tissue 33 Adenoid Reticular Tissue 33 Neuroglia 33 Cartilaginous Tissue (Hyaline Cartilage) 34 White Fibrocartilage 34 Yellow Fibrocartilage 34 Osseous Tissue 34 Dentinal Tissue 37 Epithelial Tissue 38 Membranes 39 Glands ... 40 Muscle Tissue 44 Striated Muscle 44 The Muscle Fiber . . - 45 Plain or Non-striated Muscle Tissue 47 Cardiac Muscle Tissue 49 Nervous Tissue 49 The Neuron 49 (vii) viii CONTENTS The Liquid Tissues 51 Red Corpuscles 51 White Corpuscles 51 Platelets 52 The Plasma 52 Functions of the Liquid Tissue as Related to Cells 53 Questions 53 CHAPTER HI. The Osseous System. Structure of Typical Bone 54 Classes of Bones 54 Markings on Bones 55 Muscular Attachments on Bones 55 The Bones of the Skeleton 55 The Bones of the Skull 56 Frontal Bone 56 Parietal Bone 56 Temporal Bone 56 Occipital Bone 56 Sphenoid Bone 57 Ethmoid Bone 57 Malar Bones 58 The Bones of the Trunk 59 The Spinal Column 59 The Spine as a Whole 67 The Sternum 67 The Ribs 69 Peculiar Ribs 70 The Thorax 71 The Hyoid 72 The Upper Extremity 73 The Clavicle 74 The Scapula 75 The Humerus 77 The Bones of the Forearm, the Radius and the Ulna 81 Carpal and Metacarpal Bones 88 The Bones of the Lower Extremity 88 The Os Innominatum 88 The Ilium 88 The Ischium 89 The Os Pubis 92 The Pelvis 92 The Femur 93 The Patella 96 The Tibia 97 The Fibula 99 The Bones of the Foot ... 100 The Astragalus 100 The Calcaneum 100 The Cuboid- 101 The Scaphoid 101 The Cuneiform Bones 106 The Metatarsal Bones 106 The Foot as a Whole 106 Questions 107 CHAPTER IV. The Articulations. Classes of Joints 108 The Articulations of the Vertebral Column 109 CONTENTS ix Articulations in the Upper Cervical Region 112 Articulations of the Thorax . . . . • 112 The Articulations of the Upper Extremity 113 The Sterno-clavicular Articulation 113 The Scapulo-clavicular Articulation 114 The Shoulder-joint . . . . . . . ' 115 The Elbow-joint 117 The Radio-ulnar Articulations 119 The Wrist-joint 119 The Carpal Articulations 119 The Pelvic Articulations 120 The Sacro-iliac Synchondrosis 120 The Symphysis Pubis 120 The Articulations of the Lower Extremity 120 The Hip-joint 120 The Knee-joint 123 The Articulations of the Tibia and Fibula 127 The Tarsal Articulations 128 Questions 130 CHAPTER V. The Muscular System. The Naming of Muscles 134 Movements of Muscles 134 Methods of Study 134 Movements of the Segments of the Upper Extremity 135 The Muscles Moving the Shoulder 136 Trapezius 136 Levator Scapulae 138 Rhomboideus Minor 138 Rhomboideus Major 139 Serratus Magnus 139 Pectoralis Minor 140 Subclavius 140 The Muscles Moving the Arm 140 Deltoideus 140 Supraspinatus 140 Pectoralis Major 141 Coraco-brachialis 142 Latissimus 142 Teres Major 143 Infraspinatus 144 Teres Minor 145 Subscapular is 145 The Muscles Moving the Forearm 145 Biceps Flexor Cubiti 145 Brachialis 145 Brachio-radialis 145 Triceps Extensor Cubiti 148 Anconeus 148 The Muscles Moving the Outer Part of the Forearm 148 Pronator Teres 148 Pronator Quadratus 148 Supinator 148 The Muscles Moving the Whole Hand 150 Flexor Carpi Radialis 150 Palmaris Longus 150 Flexor Carpi Ulnaris 150 Extensor Carpi Radialis Longus 152 Extensor Carpi Radialis Brevis 152 Extensor Carpi Ulnaris 152 X CONTENTS The Muscles Moving the Fingers 152 Flexor Sublimis Digitorum 153 Flexor Profundus Digitorum 153 Flexor Ossis Metacarpi Minimi Digiti 153 Flexor Brevis Minimi Digiti 156 Lumbricales 156 Extensor Communis Digitorum 156 Extensor Minimi Digiti 156 Extensor Indicis _ 156 Abductors and Adductors of the Fingers 157 The Muscles Moving the Thumb and its Metacarpal Bone .... 158 Flexor Ossis Metacarpi Pollicis 160 Flexor Brevis Pollicis 160 Flexor Longus Pollicis 160 Extensor Ossis Metacarpi Pollicis 160 Extensor Brevis Pollicis 160 Extensor Longus Pollicis 161 Abductor Pollicis 161 Adductor Pollicis 161 The Muscles of the Lower Extremity 161 Movements of the Thigh 161 Movements of the Leg 161 Movements of the Foot 161 Movements of the Toes 162 The Muscles Moving the Thigh, . 162 Psoas Magnus or Major 162 Iliacus 162 Gluteus Maximus 162 Tensor Fasciae Latae 163 Gluteus Medius 164 Gluteus Minimus 164 Adductor Magnus 165 Adductor Longus 169 Adductor Brevis 169 Adductor Gracilis 169 Pectineus 169 Obturator Externus 169 Obturator Internus 169 Pyriformis 170 Gemellus Superior and Inferior 170 Quadratus Femoris 170 The Muscles Moving the Leg 170 Sartorius 170 Biceps Flexor Cruris 170 Semitendinosus 171 Semimembranosus 171 Popliteus 171 The Quadriceps Femoris 171 Rectus Femoris 171 Vastus Lateralis 172 Vastus Medialis 172 Vastus Intermedins 173 The Muscles Moving the Foot 173 Tibialis Anterior 173 Peroneus Tertius 173 Tibialis Posterior 173 Gastrocnemius 177 Soleus 177 Plantaris 177 Peroneus Longus 177 Peroneus Brevis 179 CONTENTS xi The Muscles Moving the Toes180 Flexor Longus Hallucis180 Flexor Brevis Hallucis180 Flexor Longus Digitorum180 Flexor Accessorius181 Flexor Brevis Digitorum . .181 Flexor Brevis Minimi Digiti Pedis 182 Lumbricales182 Extensor Proprius Hallucis182 Extensor Longus Digitorum183 Extensor Brevis Digitorum183 Abductor Hallucis . . 183 Abductor Minimi Digiti Pedis185 Interossei Dorsales Pedis185 Interossei Plantares185 The Muscles of the Trunk185 The Muscles in the Third Layer of the Back185 Serratus Posterior Superior185 Serratus Posterior Inferior185 Splenius Capitis186 Splenius Cervicis 186 The Muscles in the Fourth Layer of the Back188 The Muscles in the Fifth Layer of the Back189 Suboccipital Muscles190 The Muscles of the Abdomen190 Rectus Abdominis191 Pyramidalis191 Obliquus Extemus Abdominis 191 Poupart's Ligament192 Obliquus Internus Abdominis193 Transversalis Abdominis194 Quadratus Lumborum194 The Muscles of the Thorax194 Diaphragm194 Intercostales195 Leva tores Costarum195 Triangularis Sterni196 Subcostales196 Scalenus Anterior196 Scalenus Medius197 Scalenus Posterior197 The Muscles of the Head and Neck198 Sterno-cleido-mastoideus198 Platysma . 198 Muscles of Expression198 Muscles of Mastication200 Grouping of Muscles According to Function200 Muscles Acting on the Head200 Muscles Acting on the Spinal Column200 Muscles of Respiration201 Muscles Acting on the Shoulder-girdle201 Muscles Acting on the Arm at the Shoulder-joint201 Muscles Acting on the Forearm202 Muscles Acting on the Hand at the Wrist202 Muscles Acting on the Fingers . . . ./202 Muscles Acting on the Thumb202 Muscles Acting on the Pelvis203 Muscles Acting on the Thigh at the Hip-joint203 Muscles Acting on the Leg at the Knee-joint203 Muscles Acting on the Foot at the Ankle-joint . . . . . 203 Surface Outlines of Muscles 204 to 212 Questions212 xii CONTENTS CHAPTER VI. General Consideration of Burs,®. Bursae in Relation with the Shoulder-joint 213 Bursae in Relation with the Elbow-joint 213 Bursae in Relation with the Knee-joint 214 Bursae in Relation with the Ankle-joint 214 The Fasciae 214 The Fasciae Lata 215 Annular Ligaments of the Ankle 216 Plantar Fascia 218 Connection of Fasciae and Veins 218 Questions 218 CHAPTER VII. The Nervous System. General Consideration of the Brain, Including some Special Centers . 219 The Encephalon 219 The Cortex 222 The Corpus Callosum 224 The Cerebellum 226 The Pons Varolii or Bridge of Varolius .226 The Oblongata 227 The Decussation of the Pyramids 228 Functions of the Cerebrum 229 Reflexes 230 Motor Areas of the Brain 230 Center for Speech 231 Functions of the Cerebellum 231 Functions of the Medulla 231 General Consideration of the Spinal Cord with Motor and Sensory Paths 231 The White Matter of the Cord 233 The Gray Matter of the Cord 233 Anterior Roots 234 Posterior Roots 234 White Fibers of the Cord 234 Functions of the Spinal Cord 235 Conduction 235 Association 235 Transference 236 Reflex Action 236 Reflex Arc 236 Augmentation 236 Coordination and Automatic Action 236 Special Centers 236 The Cerebrospinal Nerves and Plexi 236 The Names and Distribution of the Cranial Nerves 237 The Spinal Nerves 238 The Cervical Plexus 238 The Brachial Plexus 241 The Lumbar Plexus 243 The Sacral Plexus 249 The Sympathetic Nervous System .252 Location and Arrangement 252 Prevertebral Ganglia 252 The Sympathetic Plexi 253 Sporadic Ganglia . 253 Relation of Cerebrospinal and Sympathetic Systems 253 Relation of the Sympathetic System to the Functions of the Body . 253 The Subconscious Mind 254 CONTENTS xiii The Nerve of Special Sense, with their Sense Organs 254 The Optic Nerve and the Eye 254 The Auditory Nerve and the Ear 255 The External Ear 256 The Middle Ear 256 The Internal Ear 257 The Gustatory Nerve and the Tongue 257 The Olfactory Nerve and the Nose 257 Nerves of Touch and General Sensation 258 Questions 260 f CHAPTER VIII. The Circulatory System. The Anatomy of the Heart 261 The Pericardium 261 Columnae Camse 263 Valves of the Heart 263 The Anatomy of the Arteries 264 Divisions of an Artery 265 The Anatomy of the Capillaries 266 The Anatomy of the Veins 267 The Anatomy of the Lymphatics, Including Glands (Nodes) 267 The General Circulation of the Blood 268 The Pulmonary Circulation 270 The Systemic Circulation 270 The General Arrangement of the Arteries 270 Divisions of the Pulmonary Artery 270 Divisions of the Aorta ..... 270 Carotid Arteries 272 Subclavian Artery . .. .275 The Axillary Artery 275 The Thoracic Aorta 276 The Abdominal Aorta 276 The General Arrangement of the Veins 278 Systemic Veins 279 The Portal Vein 280 Superficial Veins of the Upper Extremity 281 Superficial Veins of the Lower Extremity 283 Long Saphenous Vein 283 Short Saphenous Vein 283 The General Arrangement of the Lymphatics and the Nodes . . .. 283 The Thoracic Duct 284 The Physiology of the Circulation 286 Systole and Diastole 286 The Cardiac Cycle 286 The Innervation of the Heart 286 Apex Beat 287 The Pulse 287 Steadying the Output of the Heart 287 Arterial Recoil 287 The Suction Pump 288 Quantity of Blood in Body 288 The Work of the Lymph 289 The Work of the Red Corpuscles 289 The Work of the White Corpuscles 289 The Blood as a Carrier 290 Clotting 290 Questions• 290 xiv CONTENTS CHAPTER IX. The Respiratory System. The Organs Concerned in Respiration 292 The Nose 292 The Posterior Nares 293 The Pharynx 293 The Larynx 293 The Epiglottis 293 The Trachea 295 The Bronchi 295 Alveoli 296 The Lungs 297 The Mediastinum 297 The Thorax 299 The Mechanism of Respiration 300 Types of Respiration 301 Ratio of Rate of Respiration, Pulse and Temperature 301 Sounds of Respiration 301 Relation of Respiration to Circulation 301 Intrathoracic and Intrapulmonary Pressure 301 Intra-abdominal Pressure 302 The Relation of Respiration to Abdominal Functions 302 Pulmonary Capacity 303 Vital Capacity 303 Residual Air 303 Tidal Air 303 Complemental Air 303 Supplemental Air 303 The Composition of Inspired and Expired Air 303 The Exchange of Oxygen and Carbon Dioxide 304 The Innervation of the Respiratory Movements 305 Questions 305 CHAPTER X. The Digestive System. The Composition of the Body 306 The Composition of Foods 307 Water 307 Mineral Salts 307 Carbohydrates 307 Fats " 308 Proteins 308 The Need for Repair and Replacement of Materials 308 The Processes in Converting Food into the Human Organism .... 308 The Chemical Changes in Digestion 309 The Organs Concerned in Digestion. The Alimentary Canal and Acces- sory Organs 311 The Mouth 311 The Teeth 311 Parts of a Tooth 314 The Uses of the Teeth 314 The Tongue 314 Salivary Glands 315 The Tonsils 316 Deglutition 316 The Esophagus 316 The Abdominal Cavity 317 The Stomach 318 CONTENTS XV The Organs Concerned in Digestion. The Alimentary Canal and Acces- sory Organs- The Stomach- The Coats of the Stomach 320 Gastric Juice 321 Action of Pepsin 321 Rennin 321 The Small Intestine . • 322 Coats of the Small Intestine 322 Villi 323 Crypts of Lieberkuhn .... - 323 Lymph Nodules 323 The Duodenum 324 Movements of the Small Intestine 326 Accessory Organs of the Digestive Tract 326 The Liver 326 The Lobule 327 Gall-bladder 329 The Pancreas 329 Absorption 332 The Large Intestine 333 Questions 333 CHAPTER XL Dietetics, Nutrition and Animal Heat. Classes of Food and How Digested 334 Requisites of a Diet 336 Animal Heat 337 Metabolism 337 Body Temperature 338 Questions 340 CHAPTER XII. X The Organs of Excretion and Elimination. The Kidneys 341 The Glomeruli 342 Uriniferous Tubules 343 The Urine 343 The Bladder 344 The Skin 345 Sweat Glands 347 Sebaceous Glands 347 Nails 348 Epidermis 348 Functions of the Skin 348 Questions 348 CHAPTER XIII. The Ductless Glands. The Spleen 349 The Endocrine System 350 The Thyroid 350 The Parathyroids 351 The Thymus Gland 352 Adrenal Gland 352 The Pituitary Body or Hypophysis 352 The Pineal Body or Epiphysis 352 The Gonads 353 Questions 353 ANATOMY AND PHYSIOLOGY. CHAPTER I. INTRODUCTION. In hygiene, both public and personal, the fundamental studies are anatomy and physiology. This is also true in the study of physical education, nursing, physiotherapy and efficient living in general. Before the significance of the above subjects can be understood, the structure, relations, mechanisms and uses of the various parts of the body must be known. It is not, however, necessary to go into all the minute details of anatomy and physiology to appreciate the wonderful way in which we live, move and have our being. A somewhat general and elemen- tary view' will serve to open the subject and possibly to interest some students to go more deeply into it. Definition.-Anatomy may be defined as the science that treats of the structure of organized beings. Organized refers to that which has distinct and different parts as compared with those that are all alike. Metals, minerals and chemical substances in general are inorganic. Plants and animals have organs, which are essential parts, no matter how few and simple they may be. Animal anatomy, or zoology, includes the structure of human beings and of the lower animals, as distinguished from that of plants or botany. The sub- divisions of zoology are called human anatomy and comparative anatomy. Physiology refers to the study of the functions of the organs in animals. The study of anatomy doubtless goes back to the infancy of the race. Every child is curious as to how things are made, and with adults the natural horror of death would be overcome by the desire to see what was inside the skin of a dead body. As bodies were examined, the various parts were given names, many of which survive to this day. These names are not always properly descriptive, as might have been the case if the parts were to be named in the present state of knowledge. They were often given on account of a fancied resem- blance to familiar obiects, as in calling the cavity in which the 17 18 INTRODUCTION Fig. 1.-English names on left side. Latin names on right side. head of the femur rests, at the hip-joint, the acetabulum or vinegar cup, etc. When some individual studied and described a part, that had not been known before, the name of that person was tacked on, as Eustachian canal, Poupart's ligament, etc. These methods make it difficult sometimes to give a reason for DEFINITION 19 Fig. 2.-English names on left side. Latin names on right side. terms, so we must fall back on the statement that certain parts are called in a certain way because they always have been so called. In beginning the study of human anatomy, it is a great help to utilize the lower animals. Specimens from the bodies of cats, chickens, lambs, etc., are invaluable in studying the tissues, as they are identical in appearance and structure with those in the human 20 INTRODUCTION animal. Even the viscera of the cat bear a sufficient resemblance to those of man to form a most useful preliminary study. Anatomy is studied either as the gross structures present them- selves or with the help of a microscope in prepared sections. This latter method is called microscopical anatomy or histology. The study of the relations of one part to another is called regional or relational anatomy. Considering the body as made up of organs, its study is called systematic or descriptive anatomy; or it may be considered with regard to the needs of the surgeon or physician, as surgical or medical anatomy. Pathological anatomy treats of the diseased states of the body and the structural changes produced. Artistic anatomy interests the artist, while applied anatomy is essential to the work of the student in physical education. The dissection of a body, that is, the careful cutting apart of its various structures is essential to a study of its make-up. The use of the roentgen rays is a modern development in scientific study and has the advantage of showing some things that cannot be seen except during life. Physiology is studied by inference from dissections, by observa- tion in the living body and more especially by experimentation on animals and human beings. The parts of the body are given technical names, mostly Latin, and have also popular or vernacular names, which may carry a different meaning. To a layman, leg refers to the entire lower extremity, but to a medical person, it means the segment between the knee and the ankle, only. In the use of anatomical terms care should be taken that they be scientifically correct, even at the risk of seeming pedantic. And, they should be spelled correctly! Names of Surface Parts.-The anatomical position, or that in which the body is studied, is supposed to be standing, with the arms at the side, and the palms of the hands facing forward. (Figs. 1 and 2.) In that position, it is possible to consider the body as being divided by three planes. The sagittal, a vertical cut through the middle from front to back, dividing the body into right and left halves. The coronal or frontal, a vertical cut from one side to the other side, which divides the body into anterior or ventral, and posterior or dorsal parts. The transverse or horizontal section, which is on a level with the horizon, and may be made at any height. Much of the relation of various parts has been learned by study of sections made by such cutting. A sagittal plane is a mesial plane, and descriptions of parts refer to their relation to that middle line, or plane. Toward it is mesial or medial; away from it is lateral. Dextral refers to the right side, while sinistral refers to the left. The transverse planes divide superior or upper parts from inferior GENERAL OUTLOOK ON RELATION OF PARTS OF BODY 21 Or lower ones. Proximal refers to that which is nearer the medial or the superior part, while distal has the opposite meaning. General Description of the Body.-The caput or head is divided into the cranium and the face. Subdivisions of the cranium are the occiput at the back, the forehead in front, the sinciput at the vertex, and the temples at the sides. The face includes the chin, cheeks, nose, eyes and mouth. Below the head is the neck (cervix or collum), which connects it to the trunk. The front is called the throat, and the back of the neck, the nape (nucha). The trunk is divided into the upper portion or chest (thorax) and the lower portion or belly (abdomen). The line of demarkation between the two is the lower border of the ribs and the lower end of the sternum, on the surface. Within, the floor of the thorax and the roof of the abdomen is formed by the diaphragm, a dome-shaped muscle. As this dome projects into the upper cavity, the thorax is smaller than appears on the surface, and the lower cavity is much larger. On the chest is a rounded mound, called the breast or mamma, much more pronounced in women than in men. About the middle of the abdomen is a puckered depression, called the navel or umbilicus. Projecting from the trunk are two upper extremities and two lower. The upper extremity presents four segments, in the follow- ing order; shoulder, arm, forearm and hand. Separating these are the shoulder-joint, the elbow-joint and the wrist-joint, in the order from above downward. The lower extremity also presents four segments; hip, thigh, leg and foot. These are separated by the hip-joint, knee-joint and ankle-joint in the order from above downward. The hip serves as a part of the wall of the abdomen, while posteriorly in the same level, is a rounded mass of muscle and fat called the buttock (natis). Back of the knee-joint is a lozenge-shaped space called the ham (poples), with the cords or tendons on the inner and outer sides known as the hamstrings. By reference to Figs. 1 and 2, other details of surface parts may be seen, with their English and Latin names. GENERAL OUTLOOK ON RELATION OF PARTS OF THE BODY. The body may be considered from many standpoints; as the temple of the soul; as a machine for doing work; as a laboratory where many materials are changed in form and chemical composi- tion and adapted for further uses, and as a servant of the mind and will. It is all of these and more, and the knowledge of its whole and its parts will repay the hours necessarily spent in the study of anatomy and physiology. 22 INTRODUCTION The more one knows about the body, the more wonderful it seems, and the more inexcusable is ignorance of its marvellous adaptation to our needs. It may sound paradoxical but it is true, that to get the best results from this study, one needs to know it all beforehand: in other words, the various parts are so interrelated to every other part that to comprehend the first part studied a knowledge of every other part is needed. The study of the muscles is bound up with that of the nerves, bloodvessels, etc. After all the divisions have been studied the student is ready to start again and really learn something. To help in getting a general view of the functions of the body, a brief account will be given here as a preliminary to more detailed work later. The Framework.-If the body is a temple, there must be a frame- work upon which the various structures may be placed for support. The most noticeable part of this framework is the bony skeleton, which is encased by many other structures, holding them so they do not interfere with others equally important. The bones form cavi- ties which contain and protect the brain, spinal cord, abdominal and pelvic organs, heart and lungs, etc., besides giving attachment to muscles and providing leverage for their action, with consequent movement of the various segments of the body. It is not the bones alone that constitute a framework. Fibrous tissue is everywhere in the body, serving like mechanical use. The individual cells, even of microscopical size, are resting in a fibrous network and if every other structure of the body were removed except the framework tissue there would be no perceptible change in its outward form. Organs that have to do with the laboratory work in the body must be supported as a whole and in their parts by fibrous tissue, the bloodvessels must have a framework and the nerves especially need protection and support. The Food Purveyors.-A temple and a machine for doing work must alike have building material for new construction and for repair of broken-down parts, and as raw material for the peculiar kind of work done. The body does much mechanical work such as moving; it does chemical work in the production of heat and energy, it transforms and elaborates materials into various other forms. These materials thus used, are provided from outside the body in the form of food. An elaborate system, the digestive organs, is concerned in preparing this food so the various cells may take it in and make it of use. process means mechanical preparation such as grinding and mixing; it means the formation of chemical reagents from the blood which act upon the food, utterly changing it in form and texture so that it may become fit to be used as building material, etc. Some of the organs so concerned are the teeth, stomach, intestines, liver, pancreas, etc., forming a long tube GENERAL OUTLOOK ON RELATION OF PARTS OF BODY 23 with accessory laboratories. Another element, oxygen, is needed in the blood and that is provided by means of the respiratory system which brings the oxygen of the air into the body. The Carrier Organs.-After the food is prepared to become a part of the tissue cells it must be taken around to them, so a system of tubes, called bloodvessels furnishes the roadway, while two pumps, one a force pump, the other a suction pump, cause the blood to be carried to all parts of the body, even to the microscopical cells. The tubes vary in size from 1 inch in diameter to those too small to be seen with the naked eye. No part of the body is without them. The food materials are thus carried to the various cells where they become a part of its structure, and are used to produce energy in the form of heat or motion, substances for the digesting of other food, and the formation of numerous other things needed in the body. In the blood carried by the tubes are not only the products from the food but the debris that results from the working of the body, or what is called waste material. These latter are taken up by the so-called organs of excretion, such as the skin, kidneys, liver, bowels and lungs, and cast out of the body, as otherwise it would be poi- soned by them. At no time is the blood free from these waste mate- rials, but if the organs work normally the amount is kept below the danger point. The Waste Removers.-The organs that remove this waste have two kinds of material to handle. First, there is the carbon dioxide which is produced during the combustion of carbon in the tissue cells. In a stove, when carbon in the form of coal is burned, heat is given off, as well as gas (carbon dioxide), and there is a residue of ashes. When carbon is burned in the body, during the working of the cells, heat or some other form of energy results, and carbon dioxide, which is poisonous to the body, is given off and must be removed. The lungs provide the means for this. Secondly, other elements, among which is nitrogen, are broken down and cast out during the working of the cells. These waste materials are called "nitrogenous," though many other elements are included. They are acted upon by liver, skin, kidneys and bowels. By the activity of these organs the blood may be said to be purified. The Organs of Motion.-If we consider the body as the servant of the mind it is evident that many forms of motion are necessary. One walks, runs and uses the arms and hands for a thousand different occupations. The muscles are these organs of motion, carrying out the orders of the mind. They are attached to the bony framework and move it. The muscles are intimately associated with the carrier organs, helping to form the suction pump which is concerned in moving the blood stream. They require a large supply of blood, and develop much heat and waste material. But they are quite 24 INTRODUCTION useless without the nerves which carry to them the orders from the brain. There is other motion going on in the body, however, than that which is under the orders of the will. In the w'alls of the bloodvessels, in the walls of the stomach and intestines, in the heart itself and in the skin, etc., are muscles that cause rhythmic movements by their contraction and so help carry on the functions of these parts as well as of all others. These con- tractions are regulated according to the needs of the tissues, under stimuli regulated by the subconscious mind, and they determine how much blood shall go through a vessel at any time, how much bile shall be secreted, how much perspiration shall come out on the skin, how regular the heart action s-hall be, and with what degree of energy the various functions of the body shall be carried on. The Master Organs.-Every large business requires a directing head, and the human body is in the same case. The great central authority is the brain, the seat of the mind and will. From here, orders go out to and messages come in from all parts of the body. Numberless branches or nerves carry these impulses, so that there is no part of the body that cannot communicate with the brain. The muscles are powerless without the nerves, and the will is impotent if the muscles cannot obey. In addition to the brain, there is a part of the nervous system which must activate the body cells that have to do chemical work, such as secreting gastric juice, saliva, etc. This is called the sympathetic system, and it is the go-between for the sub- conscious self and the tissues, or the physical representative for what has never been definitely determined to have a local habi- tation. This system of nerves is widely distributed, but the greatest masses are in the abdominal cavity, and are known as the solar plexus, the renal and aortic plexi, etc. Smaller aggregations are in front of the spinal column. The name "abdominal brain" is sometimes given to this part of the master organs, but it is not fully descriptive. We know little of how to affect this system, but there is, without doubt a close relationship between the conscious mind and that which regulates this other essential part of living. Another set of organs that may well be classed as among the "master" organs, are the so-called "ductless" glands. Much remains to be discovered about these glands which secrete peculiar mate- rials from the blood, and then let them go back into it. Or, which might be said to act as laboratories making most potent products, in secrecy, and then putting them back into the stream of raw material. The secretions have a wonderful influence upon the growth and development of body and mind, and exert powers of which the extent is, at present, unknown. PROPERTIES OF A LIVING BODY 25 The Reproductive Organs.-The adult animal is provided with organs that have to do with perpetuating the species. These distinguish the male and female, and while present at birth, they do not develop into functional maturity until about the thirteenth year. Secretions from these organs are apparently necessary for the proper development of the entire organism during the years of adolescence, or from the age of twelve to twenty-five years. Dis- eased conditions of these organs have a far-reaching effect upon mind and body. PROPERTIES OF A LIVING BODY. The principal facts in anatomy have been obtained by the study of the cadaver or dead body, but those of physiology have been learned from the living body. There are similarities between these two, but some essential dif- ferences which should be considered here. First, in the matter of consciousness. The dead body has abso- lutely no consciousness of its surroundings, and at times a living body seems equally so. A person in a faint is oblivious to every- thing about him, but sooner or later he comes out of the faint and is more or less conscious of what is going on about him. So, a living body is said to possess more or less consciousness. The living body may feel cold, but it is not of the same tempera- ture as its surroundings, which does characterize the dead body. A temperature of 30° F. in the surrounding atmosphere would freeze a dead body, so it would register the same. But, the living body would maintain a relatively high temperature under the same con- ditions, and would register about 98° F. This would be no more if the surrounding temperature went to 110° F. The temperature of the living body would not go up to correspond, but would remain at the normal. We may command the dead body to move, but it neither hears nor obeys. We may use electrical stimulation but no response is obtained. The body remains perfectly inert. But even when the living body is unconscious it still possesses the power of movement, of spontaneous movement, and it will respond to electrical and other stimuli. These properties of the living body imply the power to adjust itself to its surroundings. Life has been defined as the continuous adjustment of one's self to his surroundings. It is not a poor defini- tion from the standpoint of physiology. The essential properties which enable the body to do this may be described in anatomical terms as- 1. Irritability, or the power to respond to external stimuli. 2. Contractility, or the power to move from place to place. 26 INTRODUCTION 3. Metabolism, or the power to take in food, build it up into its own structure, and thereby grow, as well as eliminating the waste products. 4. Function, or the power to do some sort of work. 5. Reproduction, or the power to make new individuals of its own kind. These are fundamental in every living body, and in the minute divisions of the body. By the aid of the microscope, it has been found that we are made up of numberless minute cells, each of which possesses the above properties to a greater or less degree. THE CELL. There is now to see just what is meant by a cell, and it may be briefly defined as a minute mass of protoplasm, with a nucleus. It may or may not have a cell wall; it may or may not have one or more nucleoli. Fig. 3.-Diagram of a cell. (Gerrish.) The essential parts are the living protoplasm and the nucleus. Protoplasm is the physical basis of life, and is a jelly-like material when examined in life. But, the process of preparing it for micro- scopical examination kills it so it is difficult to determine its structure. There may be a netw ork of fibers with the fluid portion contained in it, and the nucleus may also have a network. It may be the protoplasm is granular or the granules seen in working cells may be material that has been taken in to be used to make the peculiar secretion of the cell. The nucleus is essential to a living cell as no reproduction can take place without it. Chemically speaking the contents of the cell are: Water, salts and organic substances. There are twelve salts in the body, the most plentiful of which is sodium chloride. The organic substances consist of a little phosphorus, some sul- phur and proteins, which contain carbon, hydrogen, oxygen and nitrogen. THE CELL 27 A typical cell is spherical in shape, having a thickened portion, the nucleus, near the center, with the nucleoli showing as darker spots in the nucleus. Near the nucleus or in it is a small spheroidal body called the centrosome. This shows rays proceeding from its center. The centrosome divides in making new cells. Single-celled organisms constitute the lowest forms of life. One of these, the amoeba may be studied to show how a single cell will exhibit the properties of living bodies. The amoeba floats around on the water, as an irregular mass of protoplasm with a nucleus. This mass frequently throws out a long process, and by drawing the rest of itself up to the process changes its location. It has moved, thus proving it possesses the power of contractility. In its aimless movements it may come in contact with something that it recognizes as possible food. That response constitutes irritability. The organism throws out processes, and gradually surrounds the stray particle, and if it is not suitable for food, it unfolds itself and leaves it. If it is fit for food, it stays until it has taken the particle into itself and grown larger. This shows Fig. 4.-Amoeboid movements. (Hackel.) the property of metabolism. When it has become large enough, it divides into two parts so that it has become two units, that is, it has reproduced itself. Notice the way in which the amoeba moves by throwing out a slender process and moving the rest of its fluid mass up to it. Cer- tain cells in the body possess the power of moving in just this way, so they are said to possess the power of "amoeboid movement." Cells are always derived from cells, so the beginning of existence for us must have been as a cell. This cell from which the wonderful human body comes is called the ovum. The ovum possesses in some degree all the above properties of life, and after it is fertilized it divides and subdivides until a large number of cells are formed. Differentiation of Cells.-As the cells increase in number, they separate into layers that have some function especially developed. That is, certain cells will be called upon to specialize in contractility, others in irritability, others in secretion, etc. The process is comparable to a community in which every indi- 28 introduction vidual must eat, have shelter and be clothed, and where instead of each one getting his own food, building his own shelter and making his own clothing, certain ones do all the work connected with the food; others do all the building and still others have charge of the clothing. So the various needs of the community are met by the specialization of its members, and the work is done more perfectly. The higher the scale of civilization, the more one sees of such limi- tation of work to one thing. The higher the grade of living beings the more definitely the cells are specialized and the more impossible it becomes for different kinds of cells to exchange work. Aggregation of Cells.-In the developing human embryo the first aggregation of cells is into three layers, from which by further and constantly increasing differentiation are finally developed all tissues and organs. Each layer gives rise to its own particular group of tissues. The Intercellular Substance.-The cell is the actual working unit of the body, and from it is developed a substance that lies outside of it, known as the intercellular substance. This varies in amount, sometimes being only enough to unite the cells or it may predomi- nate as in some forms of connective tissue. The association of a particular type of cell with a particular type of intercellular substance is called a tissue. The association of tissues to form a definite structure, to perform some definite function, is known as an organ. The association of several organs to perform some definite work, is known as a system. For instance, the teeth, stomach, liver, pancreas and intestines are organs that help to form the digestive system. QUESTIONS. What is the "anatomical position?" What constitutes the framework of the body? Why should the body require "food purveyors?" What is the relation of the bloodvessels to other parts of the body? Can you compare the body to a furnace? If so, how? How do animals differ from plants? State your understanding of "master organs." What is the unit of body structure? What is a "cell?" Which of the fundamental properties of a living body do cells possess? Do all cells possess these properties in equal degree? What is differentiation of cells? What is a tissue? What is "amoeboid" motion? CHAPTER II. THE TISSUES OF THE BODY. In spite of the great variety of appearance of different parts of the body, they may all be grouped under five heads as belonging to five separate tissues. Connective tissue is the lowest grade and has much intercellular' material and few cells. Epithelial tissue, the next higher grade has little intercellular substance and many cells. Blood, the liquid tissue has about an equal division of cells and intercellular substance. Muscular tissue has little intercellular substance. Nervous tissue has little intercellular substance, and with mus- cular tissue is the highest grade tissue in the body. The place of an animal in the scale of existence is determined by the extent and complexity of its nervous system. The Shape of the Cells.-In the different tissues the shape of the cell is modified by the work performed. In other words, function determines structure, and structure determines function. The typical cell is a spherical mass. In epithelial tissue this is modified by pressure, into many forms. In muscular tissue it develops into a long cylindrical cell, more like a section of cord, and suitable for pulling on the bones. In nerve tissue where there must be intimate communication between the various cells, there are many processes or branches. In the liquid tissue, the solid cells must float in the liquid, so these are either spherical or flattened like disks. CONNECTIVE TISSUE. 1. Fibrous. White fibrous tissue. Yellow-elastic fibrous tissue. Areolar tissue. Adipose tissue. Gelatinous tissue. Adenoid reticular tissue. Neuroglia. 2. Cartilaginous. True hyaline cartilage. White fibrocartilage. Yellow fibrocartilage. 3. Osseous. 4. Dentinal. 29 30 THE TISSUES OF THE BODY The above are the mechanical tissues, or those that support all the other kinds. There is no part of the body into which the con- nective tissues do not enter, so that if every other tissue were removed the shape of the body would remain exactly as it was before. White Fibrous Tissue.-The framework of bones serves to support the muscles and enclose delicate organs. The cartilaginous material pieces out some of these uses, besides making the joint surfaces smooth. But the fibrous form of connective tissue, binds muscles to bones by tendons; binds bone to bone, by ligaments; covers and unites muscles, by fascia; forms the framework for all the organs of the body and with a fine mesh sews everything together. If you can get a piece of the small end of a leg of lamb, such as the butcher usually throws away, you may see several of the forms of connective Fig. 5.-White fibrous tissue (Gerrish.) Fig. 6.-Cells of white fibrous tissue, often called connective-tissue cells. (Gerrish.) tissue. Or the leg of a chicken will do equally well. On the outside of the meaty part (which is muscle), you will notice a white covering which is very tough. It is difficult to detach from the flesh, and if you tease it with a fine needle, it is seen to be made up of fine white threads woven into a sheet. This is white fibrous tissue, very strong, flexible but not elastic. It is used where these qualities are required as in tendons, which unite muscle to bone; in ligaments which unite bones to bones at joints; in sheaths that cover muscles as fascia, dipping down between them as intermuscular septa; in the capsules that cover various organs, holding them firmly and in their own place, and forming shelf-like processes which support organs like the liver and intestines. White fibrous tissues forms a part of the covering of bones, as peri- osteum. By cutting down on the specimen from the butcher you CONNECTIVE TISSUE 31 may see how strong it is and how closely applied. Under the micro- scope, fibrous tissue is found to consist of very fine fibrils, placed side by side in wavy bundles. A few cells are present, but they do not appear unless the preparation is suitably stained. Yellow Elastic Tissue.-This is the fibrous tissue that is strong, flexible and elastic. It is not fitted to be used in tendons, because it would allow the bones to get out of place dur- ing muscular contractions. It is useful in places where it is necessary to have parts return to their original position after being moved away. It is combined with cartilage in the pinna or external ear, and is plentiful in the ligamentum subflava, connecting the laminae of the vertebrae. Microscopically, yellow elastic tissue consists of rather thick and branching fibers, which curl up at the ends where they are broken. Areolar Tissue.-If the student will now take the fragment of meat, referred to, and gently pull the fibers apart, it will be seen there are numberless very fine threads holding them together. The threads resemble a spider's web for fineness and delicacy, and on looking carefully, they can be seen everywhere sewing together the larger ele- ments. Minute spaces between the threads give the name to this tissue though these are not definitely walled. They communicate freely with each other and are bathed in a lymph fluid which increases their flexibility. (When any part of the body is injured, the swelling which follows is usually due to the increase of fluid in the areolar spaces.) Areolar tissue is found under the skin, connecting it with the underlying tissues; forming a bed for bloodvessels; a bed for nerves; among bundles of muscle tissue; and in the spaces about other kinds of cells, as in glands. It is attached to deeper structures on one side and to the superficial structures on the other. When one of these is moved the areolar tissue allows it to slide for a short dis- tance, by stretching the yellow-elastic fibrous tissue and straighten- ing the wavy bundles of the white fibrous tissue. The skin may be pulled quite a distance and then return to its former position by the yellow elastic fibers drawing the white bundles back to their wavy condition. The microscopical appearance of areolar tissue, as illustrated, shows a combination of white fibrous bundles and yellow elastic fibers in a network around it. Fig. 7.-Yellow fibrous tissue. (Queckett.) 32 THE TISSUES OF THE BODY Adipose Tissue.-This is a modification of areolar tissue, in which the spaces are filled with oil or fat. The connective tissue cells Fig. 8.-Areolar tissue, composed of bundles of white fibrous tissue and branched strands of yellow fibrous tissue loosely intertwined. (Gerrish.) undergo a degeneration or metamorphosis in which little sacs of oil are formed which are deposited in the areolar spaces. This Fig. 9.-A portion of areolar tissue inflated and dried, showing areolae. (Gerrish.) tissue is practically everywhere, with a few exceptions. It varies in amount, and is sometimes present to a dangerous degree. It CONNECTIVE TISSUE 33 serves as a cushion for organs, as the eyeball and kidney; being a slow conductor of heat, it is a protection against cold; it is a reserve supply of food, and adds grace to the form by rounding out what would otherwise be angles. Gelatinous Tissue.-This is an immature form of fibrous tissue with a network enclosing a semi-fluid material. The vitreous humor of the eye is an example of this tissue, where it maintains the shape of the eyeball, preventing the wrinkling of the retina (the spread- out optic nerve) as this would blur the sight. Fig. 10.-Adenoid reticular tissue. (Gerrish.) Adenoid Reticular Tissue.-This form of fibrous tissue serves as a framework for the irregular masses of leukocytes (white blood cor- puscles) which are the active portions of lymphatic nodes, sometimes called lymphatic glands. It is also plentiful in mucous membranes. Fig. 11.-Neuroglia cells. (Gerrish.) Neuroglia.-This is a network that supports the nerve substance of the brain and spinal cord. It is not true white fibrous tissue, but is made up of glia cells and their branching processes. These cells are irregular and star shaped with their branching ends frayed out in minute fibrils w'hich go everywhere between the nerve cells and the fibers. 34 THE TISSUES OF THE BODY Cartilaginous Tissue (Hyaline Cartilage).-This is composed of a very few cells and much intercellular material. It is bluish-white, dense, smooth and elastic. It covers the joint surfaces of all bones, serving as a buffer and lessening friction; it is placed between bones as a buffer; it connects the ribs with the sternum, adding much elasticity to the thoracic cage; it forms the larynx and most of the nose; and it is the material which keeps the trachea and bronchi from collapsing, so the air may pass through without hindrance. It is covered with a protective and nutritive coat, called perichon- drium. White Fibrocartilage.- This is a combination of hyaline cartilage and white fibrous tissue. It is tough, elastic and flexible, and is used to give elasticity to certain structures, as when placed between the bodies of the vertebrae as the intervertebral fibrocartilages. Yellow Fibrocartilage.- This is a combination of yellow elastic tissue and hyaline cartilage. It is markedly more elastic than hyaline cartilage. It is used to form the epiglottis, etc. Hyaline cartilage is either temporary or permanent. In fetal life, the long bones are laid down as rods of cartilage, and as the bone salts are deposited in them, the cartilage is replaced by bone. This is the temporary form. The cartilage on the articular surfaces of bones is always cartilage, and undergoes no change. Osseous Tissue.-Bone is the form of connective tissue that is of the hardest consistency, exceeded in hardness by two materials only, the dentin and enamel of the teeth. The hardness of bone is due to the deposition of inorganic sub- stances in the intercellular matrix. These materials are mainly the phosphate and carbonate of lime, though small quantities of other salts are present. These salts are so intimately combined with the osseous structure that though they compose two-thirds of the weight of the bone, they cannot be distinguished as separate by the use of the most powerful microscope. If the specimen of bone from the butcher is examined, it will be noticed that the bone is pinkish in color, is covered with a thin membrane (the periosteum), and the sawed end shows it to be a hollow cylinder. A pinkish material is in the center (marrow), but if the bone is mature this marrow is yellow. If the specimen is dissected and the joint end exposed, it will be seen to be covered with an opaque, bluish-white material which is cartilage. A thin slice of this may be cut off and examined. Now, if the enlarged end is sawed through, it apparently consists of a spongy structure (cancellous bone), with the spaces filled with a pinkish (red) marrow. (See Fig. 12.) Comparing this bone with that of the cylindrical end, it is evi- dent that bone exists in two forms. On the outside of the bone 35 CONNECTIVE TISSUE and forming the hollow shaft the bone is very solid. This is compact bone, very strong and heavy. If the entire bony skeleton were of this compact bone, our weight would be so much increased it would be necessary to have much larger and stronger muscles to move the body. To secure the necessary strength without undue weight, the shafts of the long bones are hollow and the expanded ends are made of cancel- lous or spongy bone which is very light in weight. The specimen from the butcher shows bone as it exists in the body, the so-called "recent state." The dry bones gener- ally used in the study of anatomy, have had all the soft tissues removed, making them much pleasanter to handle. Bone consists of animal and mineral matter, 36 per cent of the former and 64 per cent of the latter. When the animal matter has been burned out, the bone remains of the same shape, but is very brittle, crumbling easily. If the mineral matter is removed by soaking in dilute acid, the shape is not changed, but it has no rigidity. It may be bent and twisted in any direction. The ap- pearance under the microscope remains the same in both cases. It is in the minute structure that the essential life of bone is carried on. Like the other forms of connective tissue it is made of cells and intercellular sub- stance, of which the latter predominates. The working, part or cells are ovoid in shape, nucleated and with numerous small processes. These cells lie in spaces called lacunoe (little lakes). From the lacunae pass minute canals (canalicuW) which join with those from other lacunae, so there is a complete system of little canals through which passes the nutri- tive materials. The intercellular substance is in fibrous layers in which the mineral salts are deposited. These layers are called lamelloe. By reference to Fig. 13 the plan of the structure of bone may be seen in detail. The Haversian systems are seen in Fig. 14 under slight Fig. 12.-Diagram of recent bone. 36 THE TISSUES OF THE BODY Fig. 13.-Diagram of the structure of osseous tissue. A small part of a trans- verse section of the shaft of a long bone is shown. At the uppermost part is the periosteum covering the outside of the bone; at the lowermost part is the endosteum lining the marrow cavity. Between these is the compact tissue, consisting largely of a series of Haversian systems, each being circular in outline and perforated by a central canal. In the first one is shown only the area occupied by a system; in the second is seen the concentric arrangement of the lamellae; and in the others, respectively, canaliculi; lacunae; lacunae and canaliculi; the contents of the canal, artery, vein, lymphatic and areolar tissue; lamellae, lacunae and canaliculi; and, finally, all of the structures composing a complete system. Between the systems are circumferential and intermediate lamellae, only a few of which are represented as lodging lacunae, though it is to be understood that lacunae are in all parts. The periosteum is seen to be made up of a fibrous layer and a vascular layer, and to have upon its attached surface a stratum of cells. From the fibrous layer project inward the rivet-like fibers of Sharpey. (Gerrish.) CONNECTIVE TISSUE 37 enlargement. The small dots seen on the sawed end of bone are the Haversian systems with the canals in the middle. In the shaft of a bone, one or more rather large holes are seen through which pass the nutrient artery. Other openings (foramina) which serve the same purpose are seen near the expanded ends. Fig. 14.-A, transverse section of a long bone, natural size; B, the dark part of A, magnified 20 diameters. Haversian systems of different sizes are seen, with canals, lamellae and lacunae. The enlargement is not sufficient to show canaliculi At b is a portion of the cancellated tissue. (Peaslee.) The periosteum is made up of two layers, the outer fibrous, and the inner consisting of a network of capillaries and osteogenetic cells. These latter are epithelial cells that secrete from the blood the materials that make bone. Growth and repair of bone take place by means of the periosteum, If any considerable portion of this is destroyed, the unprotected portion of bone dies. From the fibrous layer of the periosteum go prolongations into the bone that are called "Sharpey's fibers." They attach the periosteum firmly to the bone. Dentinal Tissue.-This makes up the bulk of the tooth substance and is covered by a still harder material, the enamel. It is similar to bone, but instead of having the Haversian systems, there are radiating tubules that carry the nutritive materials. 38 THE TISSUES OF THE BODY EPITHELIAL TISSUE. If we look at our own skin, we see a good example of this tissue, for while the skin contains other tissues, it is essentially an epithe- lium. The lining of the nose, mouth, eyelids, ears and the covering of the tongue are likewise epithelium. We find that every free surface of the body, including the internal organs is covered with this tissue. Every cavity is lined with it. If-the skin is broken or a part of it is brushed off as in a burn or blister, we realize what a protection this epithelial tissue is to the sensitive underlying parts besides preventing the escape of the fluids within. If we touch the lining of the mouth we realize how this tissue imparts smoothness to surfaces, this is true also of the lining of bloodvessels and cavities in the trunk and cranium. In the mouth is a fluid named saliva that is always present, no matter how much may be used in mostening food. It is made by the epithelial cells in the salivary glands. These are like little fac- tories, taking the materials brought by the blood and manufacturing something different. This making of secretions is exclusively the property of the epithelial cell, providing different secretions for every use. The gastric juice, the bile, the fluid in the brain and spinal canal, the wax in the ear, etc., all are made by the epithelial cells. When food has been transformed into such a state that it can become a part of the blood, the epithelial tissue attends to trans- ferring it from the alimentary tract to the bloodvessels. Certain cells have waving processes (cilia) that keep the fluid with which they are in contact moving along, carrying it toward the exterior of the body. It is in this way that mucus in the bronchial tubes is carried to the place where it can be coughed up and expectorated. And, lastly, by this tissue certain sensory impressions, as those brought to the ear, are helped to be appreciated by the brain. All this work mentioned above is done by cells of microscopical size and of varying shapes. The typical epithelial cell is spherical with a rather large nucleus, resting on a delicate connective tissue, basement membrane. The cells are held together by a very small amount of intercellular substance called "cement" substance. There are no bloodvessels in the tissue, but it is supplied by loops of capillaries coming up to the basement membrane. It is scantily supplied with nerves. This tissue after being destroyed is quickly replaced. The skin, as an instance, heals in a short time after being broken. Spherical cells are not usually seen as they would require too much room, so they are crowded together, with the shape being changed according to the direction of the pressure. If the pressure is sideways, the cells become tall and like columns, forming columnar or cylindrical EPITHELIAL TISSUE 39 cells. If the pressure is from above, they are flattened, as in pave- ment or squamous epithelium. If it comes from all sides the cells become polyhedral. A few modifications of these forms should be considered. Ciliated columnar cells have delicate processes projecting from their free surfaces, which move constantly, waving back and forth with a stronger motion in the direction toward the surface of the body. They keep fluids moving and are numerous in the respiratory tract, and in a few other locations. Pigmented cells are irregular in shape and contain dark particles called pigment. They give the dark color to the skin and some other structures. In the skin this pigmentation protects the sensory nerves against the light. Fig. 15.-Two conoidal epithelial cells, their free ends furnished with cilia. (Gerrish.) Fig. 16.-Goblet-cell, surrounded by cylindrical cells. (Gerrish.) Goblet or chalice cells are specialized columnar cells found in mucous membranes. In these cells the nucleus is usually about the middle, but when activity begins it sinks to the bottom, the cells fill with granular material which swells, making them larger and crowding those nearby. Finally, the pressure within becomes so great, the cells break and their contents comes out on the surface as mucus. Glandular epithelium is composed of cells of varying shapes according to the shape of the cavities to which they adapt them- selves. Membranes.-Epithelium may be in a single layer or in several layers (stratified). A number of cells arranged in one or more layers is called a membrane. The skin has a number of layers, one above another, the structure being called a cutaneous membrane. When an epithelium imparts smoothness to a surface, or covers it and forms a secretion on such surfaces as communicate with the outside air, the structure is called a mucous membrane. Under similar conditions if the surface does not communicate with the outer air, the structure is a serous membrane. The lining of the 40 THE TISSUES OF THE BODY mouth and of the stomach are examples of mucous membranes, while the covering of the lungs and heart form serous membranes. The epithelium that lines the capsular ligament of joints does not communicate with the air, so it is similar to the serous membrane, but it is given a special name, synovial membrane. It secretes a fluid called synovia for lubricating the joints. Fig. 17.-Glandular epithelium as seen in a salivary gland. At the lower right-hand corner is a duct lined with conoidal epithelial cells. (Kolliker.) There are some other situations in which synovia is found, besides the joint cavities. The tendons of muscles may rest in grooves on the bones, so these grooves are smooth-lined by synovial membrane and lubricated by the synovial fluid. These are called vaginal synovial membranes or synovial sheaths. Bursal synovial membranes line bursae. These are little sacs of fibrous tissue, placed between parts that move on each other as a muscle over a bone, one muscle over another or the skin over a bone. Their function is to impart smoothness to the surfaces and provide lubrication to prevent friction. Glands.-Glands are masses of tissue of various sizes and shapes whose function is the manufacture of special fluids from the blood. If the material manufactured is to be used again in the body, it is usual to call it a secretion, but if it is to be thrown off, it is called an excretion. The use of these terms is arbitrary and the best authori- ties tend to call both by the name secretion. This secretion may be carried from the gland by a duct to some organ. To this the name of external secretion is applied. There may be no duct, and the secretion may be returned directly to the blood, as an internal secretion. Such glands are called ductless glands. The simplest form of gland may be said to be represented by the goblet cell, which secretes mucus. It is on the surface, but all the EPITHELIAL TISSUE 41 glandular work of the body cannot be carried on at the surface, as there is too much chance of interference and injury. The next most simple arrangement is a dipping down of the surface, so a Fig. 18.-Diagram showing development of glands: A, a mere dimple in the surface; B, enlargement by division; C, enlargement by dilatation; D, a combination of B and C; E, a racemose gland; F, development of method of E; G, a single tube intricately coiled. (Gerrish.) group of epithelial cells may line a shallow tube. This would be called a "follicular" gland. The secretion is thrown out on the Fig. 19.-Compound tubular gland. The upper part is the duct; the lower is the secreting portion. (Kolliker.) surface without any special duct. But, if the upper part becomes narrowed, and the cells covering it give up their secreting function, becoming simply a lining, a duct has been formed through which 42 THE TISSUES OF THE BODY the secretion passes. The gland is tubular, and may be elaborated to any degree by branching. This is one type. Fig. 20.-Compound racemose gland. The resemblance to a bunch of fruit is very marked. (Milne-Edwards.) Fig. 21.-Diagram showing gland cells during rest. Also showing blood and nerve supply. If the dipping down becomes bulbous or globular by dilating it is called "racemose," and this is a second type. It may increase by EPITHELIAL TISSUE 43 division and subdivision and combination until it becomes a com- pound gland. A fibrous network supports and gives shape to the divisions of compound tubular or racemose glands. In the network run the Fig. 22.-Simple tubular gland Fig. 23.-Simple racemose gland, bloodvessels that supply the cells with nutriment and working material, and the beginnings of the drainage tubes that carry off the waste or excess of material. The nerves that control the work of secretion are also found in this network. (Fig. 21.) Fig. 24.-Compound racemose gland. It should be remembered that the epithelial cells are microscopical in size, a small fraction of a millimeter in diameter and all the won- derful work that takes place in them is done by the aid of other microscopical structures. Glands have working periods and resting periods. During rest, there is an accumulation of granular material in the cells. After a 44 THE TISSUES OF THE BODY gland has been working for a time, the granular material has decreased or disappeared, apparently undergoing chemical changes in forming the secretion peculiar to that gland. An increased amount of blood is carried to a working gland, and, by the same control that increased it, the amount is lessened when the gland is not working. There are two ways for the amount of activity and the quality of the secretion to vary. If the blood supply increases without additional stimulation of the cell by the secretory nerves, the secre- tion is more profuse but thinner. If the secretory stimulus is increased, with correspondingly increased blood supply, the secretion is increased in amount without change in its character. MUSCLE TISSUE. This is the tissue in which contractility is especially developed. It is found in three forms: 1. Striated, or cross-striped. 2. Smooth, or plain or non-striated. 3. Cardiac. Striated Muscle.-Striated muscle is that form of the tissue which is attached to the bony skeleton, is under the control of the will and has to do with such manifestations as are peculiar to animals, i. e., as motion. It makes a large portion of the bulk of the body and is identical with what is known in the lower animals as lean meat. The speci- men from the butcher, before referred to, should be examined to see its physical properties. In color it varies from a deep red to a pale pink, according to the amount of blood contained and the size of the fibers. It is somewhat elastic, is easily torn and is attached to the bones by means of tendons or directly through the periosteum. A coat of fibrous tissue covers every appreciable amount of it, and even its unit of structure, the fiber, is covered with fibrous material. The tendon is made up from the aggregation of the coverings extended beyond the fiber. There are various ways in which the fibers are placed in regard to the tendon. Sometimes the bundles of fibers are parallel and spindle-shaped, with the tendons at each end: the fusiform arrange- ment. Or, the tendon may be at one side with the fibers placed at an oblique angle with it. This is the "penniform" arrangement. There may be fibers on both sides of the tendon, the " bipenniform" arrangement. These arrangements vary according to the work to be done. The tendon, instead of being cord-like may form a sheet that covers much of the muscle, as an "aponeurosis." MUSCLE TISSUE 45 Or, there may be several rows of muscle fibers with lines of tendon crossing them, forming a "tendinous inscription." The Muscle Fiber.-The fiber is the unit of muscle tissue. It is cylindrical in shape, with rounded ends. On the outside is a deli- cate fibrous sheath, the sarcolemma. Fig. 25.-Part of a fiber of cross-striped muscular tissue, showing the alternating bands. (Gerrish.) If the fiber is placed under a microscope of moderate power, it appears to have cross-way stripes or striations. These give the name to this class of muscle tissue. Besides the cross stripes there are very delicate lines longitudinally. Under a high-power micro- scope, the fiber appears to be made up of a number of parallel fibrils, having long spindle-shaped processes alternating with round bead-like ones, with constrictions between them. These fibrils are the contractile portions of the fiber. When they contract, the spindles and beads shorten longitudinally and broaden transversely. Between the fibrils is a liquid material, the sarcoplasm, which is pushed aside by the change in the contractile elements, so the muscle fibers shortens and broadens in contraction. An essential part of the muscle cell or fiber is the motor nerve ending. Every cell has its motor nerve by which it is stimulated to contract. So intimate is this arrangement that it is fair to speak of a muscle fiber as a muscle and nerve combined. (Foster.) The muscle contracts after it is stimulated by the nerve, and then it rests until another stimulation occurs. Each contraction 46 THE TISSUES OF THE BODY may be compared to an explosion which follows the stimulus, and the more frequent the stimuli, the more frequent the contractions. Fig. 26.-Diagram showing the minute structure of cross-striped muscular tissue. (Gerrish.) Fig. 27.-Motorial end-plate, the termination of a nerve in a fiber of cross-striped muscle. (Testut.) If a proper apparatus is arranged, so the contractions may be shown on a paper placed on a revolving drum, some such figure as in Fig. 28 would result. It would show that the muscle does not contract the instant the stimulus is applied, but there is a time of preparation, after which the contraction occurs reaching a maximum intensity and then declining from this maximum to the end of the Fig. 28.-Curve of simple muscular contraction. contraction. This time of preparation is called the "latent" period. In Fig. 28 the time at which the stimulus is applied is indicated by"S." In a fiber are many fibrils bundled together, the fibers being grouped in a bundle, and this bundle with other bundles, until the MUSCLE TISSUE 47 bundles of bundles become a real muscle as seen in the body by the naked eye. Each successive group has its own fibrous investment. Fibers vary in length from | inch to 2 inches. In width they vary from °f an inch 1° °f an inch. If the muscle is more than 2 inches long, the fibers are joined end-to-end to make up the necessary length. Between the fibers is areolar tissue in which run the bloodvessels, including the lymphatics and the nerves. Fig. 29.-Structure of muscle tissue with arrangement of bloodvessels and nerves Plain or Non-striated Muscle Tissue.-This is the form of muscle which is not under the control of the will, but is stimulated by the sympathetic nervous system, in its work of contraction in the walls of .hollow viscera and bloodvessels. It aids in the performance of those functions that are called "vegetative." These fibers are not arranged in bundles but in sheets. The fibers run around the vessel or lengthways of it, and in the hollow viscera they may go in all directions. 48 THE TISSUES OF THE BODY The microscopical unit is the cell or fiber, which is fusiform in shape. About the middle of it is some granular material and quite a large nucleus. The size varies from to to of an inch in length, with the width a fraction of these. Fig. 30.-Cells of plain muscular tissue. (Gerrish.) Fig. 31.-Cell of cardiac muscular tissue. (Testut.) A delicate sheath covers each cell, with areolar tissue surrounding it. The color is pale, and their blood supply less profuse than is that of the voluntary muscles. Fig. 32.-Cardiac muscular tissue, the cells united in a network. (Testut.) The contraction of this tissue occurs in a long-continued rhythmic wave, which can be well seen in a freshly killed animal when a stimulus (blow) is given to the coil of intestines. This rhythmic wave in the digestive organs is called peristalsis. AWiKOt/S TISSUE 49 Cardiac Muscle Tissue.-This is a form found only in the heart. In appearance it has some of the characteristics of both the striated and non-striated muscle. It presents irregular cross-striations, but the cells are short and branched, with large nuclei. It is not under the control of the will, though it is affected much by the emotions. The cells are arranged in a network, with many open spaces, by being joined end-to-end. The blood supply is very ample. The contractions are rhythmic, with waves passing in a circular fashion around the cavities of the heart. These contractions are followed by periods of rest. NERVOUS TISSUE. This is the highest grade tissue in the body, the master tissue, and the most difficult to replace if destroyed or injured. It is found all over the body, with aggregations in the brain, the spinal cord and in the trunk in front of the spinal column. It is usually divided into gray and white nervous tissue. The gray matter is pinkish- gray in color, found on the outer surface of the brain, the center of the spinal cord, and in the masses in the trunk. It is the active part of the tissue, receiving impressions, sending orders, coordinat- ing, considering, remembering and originating impulses. It con- sists of cells. The white matter consists of fibers of gray matter covered by a coating which protects it. These fibers simply carry messages to and from the centers, but do not originate any. The Neurons.-The unit of nerve tissue is the neuron. This is a granular, pigmented, branched and nucleated cell that has always at least one long process called the axone or axis-cylinder process. This axone is prolonged as a fiber, going to some part of the peri- phery. The branching processes are called poles. These divide and subdivide into protoplasmic processes called dendrites. The axone may remain without coating as a gray nerve fiber, or it may become invested with the white coating and become a white nerve fiber. This covering is soft and oily, known as the medullary sheath or "white substance of Schwann," and it is surrounded by a fibrous sheath, the neurilemma. The medullary sheath covers the fiber except at intervals where only the neurilemma invests it. These intervals are called the "nodes of Ranvier." At its termination, the axone divides into a number of branches from which the coating is absent. Nerves as seen in the body look like white cords, of varying size. They consist of a bundle of fibers, held together by areolar tissue, in the meshes of which run the bloodvessels and lesser nerves which nourish them. Nerve fibers carry messages in two directions, either from or to 50 THE TISSUES OF THE BODY Fig. 33.-A neuron. (Stohr.) THE LIQUID TISSUE 51 the center. Those that carry from the center are called "efferent" and grow from the center outward. Those which carry to the center (afferent nerves), grow inward from the nerve cells in organs of special sense or the tactile cor- puscles (touch), etc., and their fibers branch within the nerve centers and communicate with the cells. Afferent or sensory nerves pass between the muscle cells. THE LIQUID TISSUES. This tissue is in two forms, blood and lymph. Blood is red, opaque, viscid, of a stale odor and salty taste. Its specific gravity is 1055. Its reaction is neutral unless it has been changed to acid or alka- line by diet. The temperature of blood is 98.6° F. or about 37° C. It may be higher in the deeper vessels, and in the liver is about 107° F. In amount it is about 7| per cent of the body weight. It is distributed in about equal fourths to the liver; the skeletal muscles; the heart and large bloodvessels, and the rest of the body. The blood is in a system of closed tubes, and it does not get out of them unless these are injured. The lymph may be considered as a part of the blood which has left the vessels, and gone into the spaces of the areolar tissue. These spaces are called "lymph spaces" "intercellular spaces" or "peri- vascular spaces," when considered in relation to the lymph, the cells or the bloodvessels respectively. Specimens of the lymph may be seen in the watery fluid that exudes when the skin over a blister is broken. If blood is drawn from a vessel and allowed to stand, it presently changes to a solid mass at the bottom and a straw-colored fluid on top. The liquid is the plasma, and the solid part is clot made up of corpuscles or cells caught in a network of fibrin. The plasma may be considered as the intercellular substance of this tissue, with the corpuscles as the cells. There are 1. Red corpuscles (erythrocytes), 4,500,000 to 5,000,000 per 1 cm. 2. White corpuscles (leukocytes or lymphocytes) 7000 to 10,000 per 1 cm. 3. Blood platelets (thrombocytes), 200,000 per 1 cm. 4. Blood dust (hematokonia). The red and white cells are visible under a low-power microscope, but the latter two require very high magnification to be seen. The red corpuscles are straw colored when viewed singly, and red when in bulk. They consist of 65 per cent water and 35 per cent solids. The solids comprise hemoglobin in a stroma or framework and mineral salts. The hemoglobin is a form of iron which attracts 52 THE TISSUES OF THE BODY oxygen strongly and gives the red color to the blood. It will also absorb carbon dioxide. The red cells are biconcave disks, with an average diameter of 7.5 microns, or of a size to pass through the very smallest blood- vessels in single file. They are being constantly destroyed, mostly in the liver, and new ones are being made in the red marrow of the bones. Their function is to carry oxygen. The white corpuscles are colorless, but in a mass show up white. They are spherical, larger than the red disks, contain a variable number of nuclei and by virtue of their power of amoeboid move- ment can get out of the bloodvessels into the lymph spaces. The name (wandering cells) refers to this peculiarity. Fig. 34.-Blood corpuscles. One colorless corpuscle is seen at the top; the others are colored. (Dalton.) Their work is to dispose of waste or foreign materials, including pathogenic bacteria, a process known as "phagocytosis." They are often called "phagocytes." In inflammatory conditions, the number of leukocytes is much increased. If the tissues break down, the debris and dead bodies of the phagocytes form what is known as "pus." Platelets.-These are minute round or oval bodies about 2 microns in diameter. They are said to have amoeboid movement, and to be concerned in the coagulation of the blood. The blood dust occurs in the form of small refractive granules. The Plasma.-The liquid portion of the blood consists of 90 per cent water and 10 per cent solids, besides the gases oxygen, nitrogen and carbon dioxide. The solids consist of Proteins (C.H.O. and N.) Fats. Sugars. Extractives Urea, lactic acid lecithin. Salts, mostly sodium chloride THE LIQUID TISSUE 53 In the plasma the nutritive materials from the foods are present, while the red cells carry the oxygen. Blood containing all these various elements is a carrier, taking: The products of digestion to the tissues. The waste products from the tissues. The oxygen taken in by the lungs to the tissues. The carbon dioxide waste from the tissues to the lungs. The internal secretions from the ductless glands to the tissues; and it is also instrumental in regulating the heat of the body. Functions of the Liquid Tissue as Related to Cells.-The lymph surrounds the various tissue cells, constantly bathing them. Accord- ing to the hydraulic pressure w ithin the cells or in the lymph, the cells take up their needed elements from the lymph or exude the waste material. Nutritive and w'aste materials are both present all the time. The means by which the lymph enters and leaves the lymph spaces will be discussed in the Chapter on the Circulatory System. QUESTIONS. Name the commonest forms of fibrous tissue. What are the characteristics of white fibrous tissue that make it useful as ligaments and tendons? Name the uses of cartilage. Where is it found as a temporary structure? Describe the structure of "recent bone," and tell the uses of its parts. State the uses of epithelial tissue. What are glands? Why is striated muscle tissue connected with bones instead of being in the walls of the stomach? Describe a neuron. Describe blood. What is lymph? CHAPTER III. THE OSSEOUS SYSTEM. Structure of Typical Bone.-Bones form the framework or skeleton of the body, to which the muscles which move different parts are attached; they support and protect soft parts which are concerned in the more vital functions, as the brain, thoracic, abdominal and pelvic viscera. Usually the bones that form cavities are broad and flat, while those that have to do with the leverage of muscles are elongated. Structure varies according to use, so there are three different classes of bones, flat, irregular and long. Classes of Bones.-Flat bones have outer layers or "tables" of compact bone, with an inner filling of spongy bone. The irregular bones are similarly covered with compact bone with spongy bone within, and are of such varied and irregular shapes they cannot be classified as either flat or long. Long bones, regardless of absolute length, have hollow cylindrical shafts of compact bone, with expanded ends of cancellous bone, covered with a thin shell of compact bone. The expanded ends provide increased surfaces for joints, while the hollow shafts ensure sufficient strength with little weight and provide space for certain nutritive elements as the marrow and bloodvessels. In the embryo, bones are preformed in either cartilage covered with membrane or in membrane alone. As development proceeds, bone-salts are laid down under the membrane in spots called "centers of ossification." In long bones, these centers are in the shaft and extremities. As the process proceeds the main shaft, called the diaphysis becomes entirely ossified and the extremities, or epiphyses, likewise, but until the time arrives when growth is completed a layer of cartilage, the epiphyseal cartilage, remains between them. When this is finally ossified, the bone is said to be "mature." All bones do not reach maturity at the same age. Usually between the ages sixteen and twenty-two years the various bones attain their full growth, though occasionally the process is not completed until the twenty- fifth year. Long bones increase in length by these additions at the ends, but the increase in girth or diameter occurs by the laying down of bone- salts under the periosteum. Flat bones increase in size by additions at their edges, as in the bones of the skull. The surface of bones varies much according to the age and the muscular development of the individual. As the muscular use 54 THE BONES OF THE SKELETON 55 increases the bones show more distinct roughness. (In selecting bones for study pick out those that show the various markings most distinctly.) Markings on Bones.-The markings on bones may be either ele- vations or depressions. The elevations include, tubercle, a blunt prominence smaller than a tuberosity; spine, which is a sharp prominence; process which may be an outgrowth of any shape or size; ridge, crest or line when narrow; condyle if broad and articular, and head if supported on a neck. Depressions of bone include fossa and cavity, which are more or less shallow; foramen, a hole; fissure, a narrow slit; canal, a long tube-like passage way. Muscular Attachments on Bones.-The muscular attachments to bone are denominated origin and insertion, considering origin the fixed point and insertion the movable point, but as these are fre- quently reversed in action, it is more satisfactory to consider origin as referring to the attachment nearer the center line of the body or the upper part of an extremity, and insertion that more distant from these points. No description fits all specimens as no two bones are exactly alike either in size, shape or markings. THE BONES OF THE SKELETON. The skeleton in the adult consists of 206 bones (including the small bones of the ear) grouped as follows: The bones of the head (22). 1 frontal 2 parietal 2 temporal 1 occipital 1 ethmoid 1 sphenoid 8 cranial bones 2 malar 2 lachrymal 2 nasal 2 superior maxillary 2 palate 2 turbinate 1 inferior maxillary 1 vomer 14 facial bones The bones of the trunk (52). 24 vertebrae. 1 sacrum. 1 coccyx (sometimes four or five). 24 ribs. 1 sternum. 1 hyoid. 56 THE OSSEOUS SYSTEM The bones of the upper extremity (64) or 32 on each side. 1 scapula, or shoulder blade. 1 clavicle or collar bone. 1 humerus or arm. 1 radius , i 1 ulna forearm. 8 carpal or wrist bones. 5 metacarpal or palm bones. 14 phalanges or finger bones. The bones of the lower extremity (G2) or 31 on each side. 1 os innominatum or hip bone. 1 femur or thisrh bone. 1 tibia 1 fibula 1 patella or knee-cap. 7 tarsal. 5 metatarsal. 14 phalanges or toes. The sternum is sometimes said to form several bones, hence the varied numbers of the bones in the skeleton given in different books. THE BONES OF THE SKULL. The eight bones of the cranium are so placed as to form a hollow, somewhat spherical receptacle for the brain. They are joined to each other by sutures. Frontal Bone.-Forming the greater part of the forehead is the frontal bone. The internal surface lodges the anterior lobes of the brain, or that portion said to contain the intellectual centers. Parietal Bone.-Back of this are two quadrilateral bones called the parietals, which are united by a suture in the middle of the skull called the parietal suture. Temporal Bone.-Two temporal bones situated at the sides and base of the cranium, are described as having three distinct portions, the squamous, the petrous and the mastoid process. The petrous portion contains the internal ear and the canal leading thereto, and supports the cartilaginous external ear or auricle. To the mastoid process are attached the sternomastoideus, the splenius capitis and the trachelomastoideus muscles. The squamous portion gives attachment to several muscles concerned in mastica- tion. Occipital Bone.-The posterior-inferior part of the cranium is formed by the occipital bone. On this are several points of interest. A large foramen (foramen magnum) gives passage to the spinal leg. THE BONES OF THE SKULL 57 cord as it passes from the brain into the spinal canal. Anteriorly to the foramen are two articular processes where the skull rests upon the atlas and articulates with it. The posterior surface presents a prominent process of bone called the occipital protuberance to which the ligamentum nuchse is attached. Curving outward from this on each side are the superior curved lines to which are attached the occipito-frontalis, the trapezius and splenius capitis muscles. Below the superior are the inferior curved lines, and to the space between are attached the complexus, the rectus capitis posticus major and minor and the obliquus superior muscles. Fig. 35.-Skull, viewed from the left side, showing the principal cranio-metric points. (Gerrish.) Sphenoid Bone.-The sphenoid, a bat-shaped bone, is wedged in between the bones of the base of the skull, and from the standpoint of the anatomist is very important and interesting, but, having no important muscular attachments need not be given further consider- ation here. Ethmoid Bone.-The ethmoid is a small bone that helps to form the nasal and orbital fossae. The fourteen bones of the face form the framework to which the muscles of expression are attached as well as some that have to do with mastication and deglutition. They form part of the orbital 58 THE OSSEOUS SYSTEM and oral cavities and the nose and provide sockets in which the teeth are set. Malar Bones.-The two malar bones form the prominence of the cheek; the lachrymal bones help form the canal for the tear duct; Fig. 36.-Base of the skull, viewed from below, the mandible having been removed (Testut.) the nasal bones form the upper part of the nose; the inferior maxil- lary or mandible is the lower jaw in which are the alveolar processes for the teeth, and to which numerous muscles are attached. The two superior maxillary and two palate bones form the roof of the mouth, and the former provides sockets for the upper teeth; the THE BONES OF THE TRUNK 59 two turbinated bones provide the base for a large surface of mucous membrane, while the vomer forms the lower and back part of the septum between the two sides of the nose. (Figs. 34, 35 and 36.) Fig. 37.-Sagittal section of skull, a little to the left of the middle line, the inner surface of the right half. (Testut.) THE BONES OF THE TRUNK. The bones of the trunk are arranged to form a receptacle for the thoracic and abdominal viscera, that at the same time gives protec- tion, allows for changes in size and form and provides attachments for the muscles whose actions are essential to their proper function- ing. This receptacle is somewhat cylindrical in form, incomplete in the front lower part and made up of the spinal column behind, the sternum in front and the ribs on the front, sides and back. The Spinal Column.-The spinal column is made up of twenty-six segments to provide flexibility with strength. These segments are vertebrae, either typical or rudimentary, grouped into five divisions. In the neck are seven vertebrae, called cervical; below these are twelve dorsal or thoracic vertebrae, to which the ribs are attached; below' these, five lumbar vertebrae, followed by the sacrum and that, by the coccyx. A vertebra is an irregular bone, having a body in front and an arch (neural) behind. 60 THE OSSEOUS SYSTEM The body is the large solid portion, somewhat like a half-cylinder, with a concave posterior, and convex anterior and lateral surfaces. The weight of the head and trunk, together with that of the upper extremity is borne on the column of bodies. The neural arch is joined to the body by processes called pedicles. Continuing from the pedicles are flat plates called laminae, which with the body complete the borders of the vertebral or spinal fora- men through which passes the spinal cord. Supported by the pedi- cles and laminae are seven bony processes, one spinous posteriorly, two transverse and four articular. On the upper and lower surfaces of the pedicles are notches, which become parts of intervertebral foramina when two vertebrae are joined together. Through these foramina pass the spinal nerves, branching out from the spinal cord. The spinous process projects backward in the median line at the junction of the laminae. The transverse processes project outwardly from the sides and the articular processes extend from the roots of the transverse processes. They are in pairs, superior and inferior, facing in opposite directions and articulating with those above and below respectively. Fig. 38.-Cervical vertebra, viewed from above. (Testut.) This description is of a typical vertebra, and with the exception of a few vertebrae, all these parts are found on every one, but there are distinguishing variations in the different regions. In the cervical or neck region the seven vertebrae have to provide for a greater amount of movement than elsewhere, so there are certain differences in structure. The bodies are smaller and flatter; on the upper surface are lateral lips; on the under surface, an ante- rior lip; the transverse processes are forked or bifid, with foramina for the passage of the vertebral artery; and the spinous processes are bifid and nearly horizontal. The third, fourth, fifth and sixth are typical, but the first, second and seventh are peculiar. The first cervical vertebra or atlas, is directly under the occiput, articulating with it. It has no body or spinous process, and allows the greatest possible freedom of motion between the head and the THE BONES OE THE TRUNK 61 spinal column. Two arches, dorsal and ventral, connect two lateral masses. On the upper surface of these masses are large articular Fig. 39.-The atlas, viewed from above. (Testut.) surfaces upon which the head rocks back and forth, in the occipito- atloid articulation. The articular facets on the under surface of the lateral masses are for the union with the second cervical vertebra, Fig. 40.-The axis, front view. (Testut.) the axis. The axis has a large strong body, on which is fused the body of the atlas, here serving as a pivot around which the atlas carrying the head may rotate. This process is the odontoid (tooth- like). Fig. 41.-The axis, its right side. (Testut.) The seventh cervical vertebra has a long spinous process that is not bifid. It is very prominent, hence its name, the vertebra prom- inens, serving as a landmark, 62 TIIE OSSEOUS SYSTEM The next group is the thoracic or dorsal vertebra;, distinguished primarily by facets on the bodies for articulation with the head of the rib, and facets on the transverse processes for articulation with the tubercle of the ribs. Usually the facets on the bodies are on the upper and lower borders, so that with the intervertebral car- Fig. 42.-A thoracic vertebra, upper surface. (Testut.) tilage between the bodies, the head of a rib may set into a sort of socket. The spinous processes project downward and overlap, especially in those near the middle of the group, while the laminae also overlap. The first and last of this group resemble those of the contiguous groups above and below. The overlapping of spines Fig. 43.-Thoracic vertebra, seen from the left side. (Testut.) and laminae limits extension of the spine very markedly, but does not much interfere with flexion and rotation. The lumbar vertebra; are large and heavy looking, having large oval bodies, long transverse processes and strong square looking spinous processes. They have neither bifid spines nor foramina THE BONES OF THE TRUNK 63 in the transverse processes, which would distinguish them from the cervical vertebrae, nor articular facets on the body and transverse processes, which distinguishes them from the thoracic group. Fig. 44.-Thoracic vertebra, viewed from behind. (Testut.) A large number of ligaments and muscles are attached to the vertebra?, connecting the spine to the head, to the trunk, to the upper and lower extremities. The sacrum articulates with the last lumbar vertebra and gives support to the spine as a whole. It is a modification of vertebrae, five seemingly being fused together, and lacking various character- Fig. 45.-Lumbar vertebra, viewed from above. (Testut.) istics of the typical vertebra. The bone is triangular in shape, widest above and tapering below, where it articulates with the upper bone of the coccyx. The sacrum lies obliquely, with the upper 64 THE OSSEOUS SYSTEM surface inclined forward, and forming an acute angle with the last lumbar vertebra. The upper part is called the promontory, with Fig. 46.-The sacrum, ventral view. (Testut.) Fig. 47.-The sacrum, dorsal view. (Testut.) the alee or wings on the sides. On each side are four large fora- mina, going through from front to back for the passage of the sacral THE BONES OF THE TRUNK 65 Fig. 48.-The sacrum, its left side. (Albinus.) Fig. 49.-The coccyx, ventral surface. (Testut.) 66 THE OSSEOUS SYSTEM nerves. The front of the bone is relatively smooth, but the dorsal aspect presents much roughness for the attachment of muscles and ligaments. The rudimentary spinous processes form a rough ridge. Laterally, are two ear-shaped articular surfaces, called the auricular surfaces, which articulate with the ilium. This articulation of the two bones completes the bowl-shaped cavity known as the bony pelvis. Fig. 50.-The spinal column, right lateral view and dorsal view. (Testut.) The coccyx consists of a variable number of small bones, rudimen- tary vertebrae, of triangular shape, tapering downward. In early life there may be from three to five of these, but later they are apt to fuse together. They serve for the attachment of several large muscles and aponeuroses. THE BONES OF THE TRUNK 67 The Spine as a Whole.-The spinal column is the central axis of the body, and is in the median line and posterior part of the trunk. It supports the head, the ribs and the upper extremity. The weight of these parts is transmitted through the spinal column to the lower extremities through the hip-bones with which the sacrum articulates. The average length is 27 or 28 inches, of which about a quarter is made up of the fibrocartilaginous intervertebral disks. The view from the side shows four curves from before backward. Convex forward in the cervical and lumbar regions; convex backward in the thoracic and sacral regions. The two latter are present at birth, but the other two are developed as the child assumes an upright position. The shape of the bodies determines the sacral and thoracic curves, but the intervertebral disks determine the extent of the curve in the other two regions. These curves add much to the strength and elasticity of the column, and lessen jars. No lateral curve normally exists. From the standpoint of correct posture the relations of the dif- ferent parts of the spinal column are exceedingly important. As the muscles attached to the spine connect it with every other part of the body, movements elsewhere have an influence upon its posi- tion, producing lateral deviations more or less temporary. At the junction of the cervical and dorsal spines there is a dividing point between several important muscles, with resulting weakness. This feature is much more marked at the junction of the dorsal and lumbar spines for the same reason and the additional fact that there a fixed part, the thorax joins the most movable part, the lumbar spine. A long leverage above and below with the width of the spine less than in either locality contributes to the weakness. Note.-This is easily demonstrated by holding the carcass of a fowl with one hand on the upper part, the other hand on the lower part of the trunk and bending the body backward. The spine gives way at the dorso-lumbar junction with startling ease. The Sternum.-The sternum or breast bone is on the front wall of the thorax, connecting with the ribs and the clavicle. It is a long thin bone, wider above than below, having at the lower end a prolongation of cartilage called the xiphoid or ensiform cartilage or process. The upper part of the bone is thicker and wider and is called the manubrium or "handle." It is united to the lower part by fibrocartilage and remains distinct through life. The lower part, the gladiolus or " little sword" in early life consists of four segments which later unite into one piece. The manubrium has a notch on its upper surface ("interclavicular notch") and two articular surfaces on the lateral angles for articu- lation with the clavicles. At the widest part on the side, are artic- ular facets for its union with the cartilage of the first rib. At the junction of the manubrium and gladiolus is a transverse ridge that 68 THE OSSEOUS SYSTEM Fig. 51.-The sternum, ventral aspect. (Spalteholz.) THE BONES OF THE TRUNK 69 serves as a landmark in locating the valves of the heart. Articular facets laterally give attachment to the second rib, while the next five articulate with the gladiolus. Thus seven ribs are directly joined to the sternum. The muscles attached to the sternum are, pectoralis major, sternomastoideus, rectus abdominis, the aponeurosis of the trans- versus abdominis and obliquus internus abdominis, the sternohyoid, the sternothyroid, the triangularis sterni, the internal intercostals and the diaphragm. The Ribs.-Twelve pairs of ribs form the larger part of the walls of the thorax, prolonged at the front end by plates of cartilage, the costal cartilages, which serve as buffers and increase elasticity. The upper seven pairs of ribs are attached directly to the sternum and are considered true ribs (or sternal ribs) while the next three being indirectly attached to the sternum are called false (or asternal) Fig. 52.-The sixth rib of the right side viewed from the middle line of the body. (Spalteholz.) ribs, and the last two pairs are attached to the vertebrae only and are called "floating ribs." The length of the ribs increases from the first to the eighth then decreases to the twelfth. A rib is a "long bone," having a shaft and two extremities. The middle eight ribs are typical, but the first two and last two are peculiar. At the vertebral end of a typical rib is the enlarged head which is joined by a constricted neck to the shaft. The head articu- lates with the bodies of the vertebrae. Just where the neck joins the shaft is a prominence of bone called the tubercle. This articu- lates with the transverse process of a vertebra. The shaft begins at the tubercle and extends to the sternal end where a cup-like cavity receives the costal cartilage. The shaft of the rib is curved in three directions. Looking at the back of the thorax it is seen that there is a relative fulness to the 70 THE OSSEOUS SYSTEM curve of the ribs, and that where they begin to form the side wall of the chest a sudden bend is made in the curvature. This bend is the angle and it takes place at a greater distance from the spine in the lower ribs as they proceed downward. The curvature of the front end is flatter. In addition to these curves on the flat, the shaft of the lower ten ribs at the angle is curved on the horizontal axis so if the rib rests upon the lower border of the shaft the vertebral end curves upward. This curve increases from the third to the seventh ribs, then decreases to the twelfth. This twisting is of great importance in providing for an increase of the lateral and antero-posterior diameters of the thorax in respiration. Fig. 53.-The first and second ribs of the right side, viewed from above. (Testut.) Peculiar Ribs.-The first rib is short, broad and so placed that the surfaces face up and down. It affords attachment to the sca- lenus anticus and medius muscles, and to the first digitation of the serratus magnus muscle. The second rib is longer and lacks the curve on the horizontal axis. It gives attachment to the scalenus posticus and to the second and third digitations of the serratus magnus muscle. The scaleni being muscles of inspiration act by raising these two upper ribs thus providing a firm base for the elevation of the other ribs by the intercostal muscles. The eleventh and twelfth ribs are short and lack several of the characteristics of a typical rib, as tubercle and angle. The costal cartilages are hyaline cartilage which prolong the ribs at the sternal ends, fitting into cup-like depressions on the shaft and the first seven articulating with the sternum. Their direction is upward and inward and the length increases to the seventh rib. THE BONES OF THE TRUNK 71 The cartilages of the eighth, ninth and tenth ribs unite with each other and the upper part is joined to the cartilage of the seventh rib. The cartilages of the eleventh and twelfth ribs form smooth ends. The costal cartilages give attachment to most of the muscle mentioned above as being attached to the sternum. Fig. 54.-The skeleton of the thorax, front view. (Testut.) The Thorax.--The thorax is a bony cage, roughly cone-shaped, with the top formed by the first rib facing forward and upward. The much larger base is formed by the edges of the lower six ribs converging to the xiphoid cartilage and forming the subcostal angle. Note.-Look up the studies made at the Central School of Hygiene of the Y. W. C. A., New York, in reference to the signifi- cance of the width of the subcostal angle as regards mental and vital ability. The backward curve of the ribs forms a broad furrow on the back, each side of the spinal column, the vertebral groove in which rests some of the erector spinae group of muscles. The back of the thorax is flatter than the front and allows the supine position in man, as dis- tinguished from the rounded backs of quadrupeds. The bodies of the vertebrae encroach upon the cavity of the thorax 72 THE OSSEOUS SYSTEM so the inside diameter is less than that taken externally. As far down as the seventh or even lower, the ribs are increasingly more oblique. This makes the intercostal spaces wider at the side than at the back. In inspiration they are wider than after expiration thus increasing the capacity of the thorax. At birth the thorax resembles that of quadrupeds more than that of an adult human being, being more barrel-shaped and less broad in the transverse direction. The angles have not been devel- oped and the ribs are less curved. Fig. 55.-The skeleton of the thorax, dorsal view. (Testut.) The thorax contains the organs of respiration and circulation, and not only protects them, but allows the movements necessary to their proper functioning. While each rib and vertebra has but a small range of motion, the aggregate is considerable. Many muscles, moving the arms, trunk and head and giving support to the abdominal viscera, are attached to the thorax. The Hyoid.-The hyoid is a small, light, somewhat horseshoe- shaped bone in the front part of the neck below the chin. To it the tongue and many muscles of deglutition are attached. THE UPPER EXTREMITY 73 THE UPPER EXTREMITY. The upper extremity consists of the arm, forearm and hand, con- nected to the trunk by the shoulder girdle. This consists of the clavicle and scapula. Fig. 56.-The right clavicle, upper surface. (Spalteholz.) Fig. 57.-Areas of muscular attachment, upper surface of right clavicle. (Gerrish.) Fig. 58.-The right clavicle, under surface. (Spalteholz.) Fig. 59.-Areas of muscular attachment, lower surface of right clavicle. (Gerrish.) 74 THE OSSEOUS SYSTEM The Clavicle.-The clavicle or collar-bone is a long bone having a shaft and two extremities. It is curved like the italic letter f, and extends across the upper part of the chest, horizontally from the notch on the manubrium to the acromion process of the scapula, articulating with these two processes. The inner two-thirds is cylindrical in form, while the outer third is flattened from above downward and curves backward. The shaft of the bone presents on the superior and anterior aspect of the inner half a rough place for the attachment of the sternomastoideus, and below, one for the pectoralis major. The posterior sternal surface gives attachment to the sternohyoid muscle. On the outer third are rough places on the superior surface for the deltoid muscle in front and the trapezius muscle behind. Fig. 60.-The right scapula, ventral view. (Spalteholz.) The inferior surface at the sternal end presents the rhomboid impression for the attachment of the rhomboid ligament, and the subclavian groove for the subclavian muscle. Throughout the greater part of its length the clavicle is sub- cutaneous and its outline may be followed by the finger. The extent of the muscles attached to it may be felt during their contraction. This method of studying muscles should be used whenever possible. THE UPPER EXTREMITY 75 The Scapula.-The scapula or shoulder-blade is a large flat bone, triangular in shape, presenting three angles, external, superior and inferior; three borders, superior, vertebral and axillary; and two surfaces, dorsal and ventral. It extends from the second to the seventh ribs, on the posterior part of the thorax and from its articu- lation with the clavicle at the peak of the shoulder to within 2 inches of the spine. The lower border of the inferior angle may be used to locate the seventh thoracic spine as it is in a horizontal line with the latter. Fig. 61.-Areas of muscular attachment, ventral surface of right scapula. (Gerrish.) The external angle or head has an articular surface, the glenoid fossa, for articulation with the humerus. Projecting from it toward the front is a beak-like process, the coracoid process. The -ventral surface shows a shallow fossa, with several ridges crossing it, for the reception of the subscapular muscle. Along the vertebral border of this surface is a rough ridge for the serratus magnus muscle. The dorsal surface presents a prominent ridge, the spine, which passes from the vertebral border, about one-third of the distance down, going across the bone diagonally upward, becoming heavier and wider, until near the external angle it leaves the surface and continues as a broad rough prominence, the acromion process. The posterior free border of the spine is thick and curved. It is called the crest, with upper and lower lips. 76 THE OSSEOUS SYSTEM Above the spine is a fossa, the supraspinous, giving attachment to the supraspinatus muscle. The surface below the spine, the infraspinous fossa, is depressed, and gives attachment to the infra- spinatus muscle. To the upper lip of the crest is attached the trapezius muscle, while to the lower lip is attached the deltoid muscle. The external or axillary border gives attachment above to the teres minor, and below to the teres major muscles. The internal or vertebral border of the dorsal surface gives attachment above to the rhomboideus minor and below to the rhomboideus major muscles. The superior angle and the uppermost part of the Fig. 62.-The right scapula, dorsal view. (Spalteholz.) vertebral border gives attachment to the levator anguli scapulae, while the inferior angle usually has the latissimus dorsi muscle attached. The coracoid process on the external angle is covered with an aponeurosis which gives attachment to the pectoralis minor, the coraco-brachialis and the short head of the biceps muscle. Above the glenoid fossa, is a rough impression for the tendon of the long head of the biceps muscle, while below the fossa the long head of the triceps muscle is attached. The glenoid fossa, covered with cartilage in the recent state looks upward, outward and forward. The superior border of the scapula is concave, extending from the THE UPPER EXTREMITY 77 superior angle to the base of the coracoid process. It presents the suprascapular notch, through which passes the suprascapular nerve. To the border adjacent, the omohyoid muscle is inserted. This completes a total of seventeen muscles which arise from the scapula, passing in every direction, anchoring it and guarding the shoulder- joint, besides providing for movements of adjacent parts. The only bony connection of the shoulder girdle with the trunk is at the sterno-clavicular articulation. Fig. 63.-Areas of muscular attachment, dorsal surface of right scapula. (Gerrish.) The Humerus.-The humerus (brachium) or the bone of the arm is a long bone with a shaft and two extremities. The upper extrem- ity presents a rounded head, covered with cartilage in the recent state, and articulating with the glenoid fossa of the scapula. The head is directed upward, inward and backward, at an angle of about 130 degrees. Just below the head is a constriction of the bone which is called the "anatomical neck," in distinction from the "surgical neck" below the tuberosities. (The surgical neck is so-called for convenience in designating the locality in case of fracture). The anatomical neck gives attachment to the capsular ligament of the shoulder-joint. Below this are two prominences separated by a groove, the bicipital groove. The larger and outer prominence is the greater tuberosity; the smaller and inner, the lesser tuberosity. On the latter is inserted the subscapularis muscle. On the greater Fig. 64.-The right humerus, front view. (Testut.) Fig. 65.-Areas of muscular attachment, ventral aspect of right humerus. (Gerrish.) Fig. 66.-The right humerus, rear view. (Testut.) Fig. 67.-Areas of muscular attachment, dorsal surface of right humerus. (Gerrish.) 80 THE OSSEOUS SYSTEM tuberosity are three facets, one being above, the other two posterior. To the upper facet is attached the supraspinatus muscle; to the middle facet the infraspinatus muscle and to the lowermost facet the teres minor muscle. Through the bicipital groove runs the tendon of the long head of the biceps muscle to be attached above the glenoid fossa. The groove has two lips, to the inner of which the teres major muscle is attached, and on the floor of the groove and to the inner lip the latissimus dorsi muscle is inserted. To the outer and anterior lip, the tendon of the pectoral is major muscle is attached. The shaft of the humerus is cylindrical above, flattening side- ways in the lower part. The bone has three surfaces, internal, external and dorsal, separated by internal, external and anterior borders. The internal border has a rough place near its center for the coraco-brachialis muscle. The lower part of the border becomes the internal supracondylar ridge, ending in the internal condyle. The external border extending downward from the greater tuber- osity is more marked at the lower end, becoming the external supra- condylar ridge, to which in the upper two-thirds is attached the brachio-radialis and below that the extensor carpi radialis longus muscle. The anterior border begins at the outer lip of the bicipital groove, and passes down to between the capitellum and trochlea. Just above the center of the bone on the external surface is a very rough impression for the attachment of the deltoid muscle. Below this, passing across the external border, a groove, the musculo-spiral groove, winds around the shaft of the bone downward and forward. In the groove lies the musculo-spiral nerve. Above the groove, on the dorsal surface of the humerus the external head of the triceps muscle is attached, while to the surface below, the internal head is attached. To the lower half of the anterior surface is attached the brachialis muscle. The lower extremity of the humerus is flattened from before backward, and curved forward, with prominent processes, the con- dyles, on each side. These are subcutaneous. The more prominent, the internal condyle gives attachment to a group of flexor and pro- nator muscles, namely the flexor carpi radialis, flexor carpi ulnaris, palmaris longus, flexor sublimis digitorum and pronator teres. The external condyle is less prominent and gives attachment to a group of extensor muscles and supinators, namely, the extensor carpi radialis brevis, extensor communis digitorum, extensor minimi digiti, extensor carpi ulnaris, supinator and the anconeus. Between the condyles is an articular surface, divided into two parts. The larger inner surface is the trochlea (pulley), which articulates with the head of the ulna. Above this in front is the coronoid fossa receiving the coronoid process of the ulna in forced flexion of the forearm. Back of the trochlea is the olecranon fossa, THE UPPER EXTREMITY 81 receiving the olecranon process of the ulna in extension of the fore- arm. The small inner part of the articular surface is the capitellum, for articulation with the head of the radius. The Bones of the Forearm, the Radius and the Ulna.-The ulna is the longer and is placed on the inner side. It presents a shaft and two extremities. The upper part is thickest and shows an articular surface, curved forward called the greater sigmoid cavity. This articulates with the trochlea of the humerus. Below this is the coronoid process which gives attachment to the brachialis and to slips from the flexor sublimis digitorum, pronator teres and the flexor longus pollicis muscles. Posteriorly is the heavy olecranon process, the highest part of the bone, to which the triceps muscle is attached on the upper sur- face. The olecranon is mostly subcutaneous and is the most promi- nent part of the elbow. Continuous with the greater sigmoid cavity, on the outer side is a smaller articular surface, the lesser sigmoid cavity, in which the head of the radius turns in pronation and supination of the forearm. The shaft becomes smaller as it descends, though the upper part is triangular, showing definitely three borders and three surfaces. The external or interosseous border gives attachment to the inter- osseous membrane, and divides into two lines above, passing to the ends of the lesser sigmoid cavity, and enclosing a triangular space on which the supinator muscle is attached. The anterior surface gives origin to the flexor profundus digitorum muscle in the upper three-fourths. The pronator quadra tus muscle covers the lower fourth. The posterior border is partly subcutaneous and gives origin to an aponeurosis common to the extensor carpi ulnaris, flexor carpi ulnaris and flexor profundus digitorum muscles. The internal sur- face in the upper part gives attachment to the flexor profundus digitorum muscle. The upper fourth of the dorsal surface shows a triangular area on which is inserted the anconeus muscle. Below this on the inner side is an attachment of the extensor carpi ulnaris muscle, while on the outer part of the surface, from above downward, are the extensor ossis metacarpi pollicis, extensor longus pollicis and extensor indicis muscles. The lower extremity is small with a rounded head, the lower sur- face of which moves upon the triangular fibrocartilage of the wrist- joint. On the outer side is a facet that articulates with the sigmoid cavity of the radius. On the inner side, the bone is prolonged down- ward as the styloid process. The radius takes but little part in the elbow-joint but is con- cerned in the wrist-joint. The upper extremity has a head, some- what disk-shaped, with a cup-like cavity above, which articulates with the capitellum of the humerus. The side of the head articu- 82 THE OSSEOUS SYSTEM lates with the lesser sigmoid cavity of the ulna. Below the head is a rough prominence, the bicipital tuberosity, to which the tendon of the biceps muscle is attached. The shaft of the radius is triangular and increases to a much greater size below. It presents three surfaces and three borders. To the internal border is attached the interosseous membrane. Fig. 68.-The bones of the right forearm ventral view. (Testut.) Fig. 69.-Areas of muscular attach- ment, ventral aspect of the radius and ulna. (Gerrish.) Passing from the bicipital tuberosity outward on the ventral sur- face is an oblique line which gives attachment to the flexor sublimis digitorum muscle. On the middle two-fourths of the anterior sur- face of the shaft is the flexor longus pollicis muscle. On the lower fourth the pronator quadratus muscle is attached. An oblique line on the dorsal surface with that on the front, bounds an external THE UPPER EXTREMITY 83 surface to wdrich the supinator muscle is attached. Midway on the external surface is a rough impression for the pronator teres muscle. The dorsal surface in the middle third gives origin to the extensor ossis metacarpi pollicis and the extensor brevis pollicis muscles. The lowrer extremity is much larger than the upper and is some- what quadrilateral in form. Inferiorly is a cartilage covered sur- Fig. 70.-The bones of the right forearm, dorsal view. (Testut.) Fig. 71.-Areas of muscular attach- ment, dorsal aspect of radius and ulna. (Gerrish.) face with which two carpal bones, the scaphoid and semilunar, articulate. On the inner surface is the sigmoid cavity for the articu- lation with the head of the ulna. The external surface is prolonged downward into the styloid process, to w hich is attached the brachio-radialis muscle. 84 THE OSSEOUS SYSTEM Fig. 72.-The bones of the right hand, palmar aspect. (Spalteholz.) THE UPPER EXTREMITY 85 Fig. 73. -Areas of muscular attachment on the palmar surface of the bones of the hand. Where the areas of origin and insertion are both presented they are in the same color. INS., insertion; FL.O.M.M.D., flexor ossis metacarpi minimi digiti. (Gerrish.) 86 THE OSSEOUS SYSTEM Fig. 74.-The bones of the right hand, dorsal aspect. (Spalteholz.) THE UPPER EXTREMITY 87 Fig. 75.-Areas of muscular attachment on the dorsal surface of the bones of the hand. Where the areas of origin and insertion are both presented, they are in the same color. INS., insertion. (Gerrish.) 88 THE OSSEOUS SYSTEM When the hand is supine, the radius and ulna are parallel, but the radius crosses over the ulna, during pronation. Carpal and Metacarpal Bones.-The bones of the hand consists of eight carpal, five metacarpal and fourteen phalanges. The carpal bones are arranged in two rows, named from the radial side inward, scaphoid, semilunar, cuneiform and pisiform in the upper row. Trapezium, trapezoid, os magnum and unciform in the lower row. Articulating with the lower row are five metacarpal bones, numbered from the radial side inward, the first being that of the thumb. Two phalanges form the skeleton of the thumb, while each finger has three. Many muscles are attached to the bones of the hand. See Figs.. 63-75. THE BONES OF THE LOWER EXTREMITY. The skeleton of the lower extremity consists of the bones of the hip, thigh, leg and foot. A sesamoid bone, the patella, is included. The Os Innominatum.-The hip-bone, or os innominatum is an irregularly shaped bone, having more resemblance to the blade of a ship's propeller than to anything else. It is expanded above and below but narrower in the middle, where the deep socket for its articulation with the femur is seen. This socket, the acetabulum, is cup-like and in youth shows the epiphyseal lines separating the three parts of which it is made. The cavity is covered with car- tilage, except for a mass of fat at the bottom, and the rough impres- sion for the ligamentum teres muscle. The lower part of the rim is incomplete, forming the cotyloid notch, which is bridged over by the transverse ligament, forming the cotyloid foramen. The expanded upper part of the os innominatum forms the "false pelvis," a part of the wall of the abdomen, while the lower part forms the front and side walls of the "true pelvis." The weight of the trunk, head and upper extremities is trans- mitted to the lower extremities through the hip-bone. The three parts of the bone are the ilium, ischium and os pubis, separate in early life but united in adult years. These will be considered in turn as more convenient to describe and more easily comprehended than the bone as a whole. The Ilium.-The ilium presents a broad, flat and triangular appearance with a sinuously curved upper border, and narrowing to the lower part which occupies nearly two-fifths of the cavity of the acetabulum. The upper border or crest is subcutaneous, with two prominent processes at the ends, that in front being the anterior-superior spine, giving attachment to Poupart's ligament, while just below this the sartorius and tensor fascia lata muscles are attached. The crest ends posteriorly in the posterior-superior spine, which gives attachment to a ligament of the sacro-iliac joint. THE BONES OF THE LOWER EXTREMITY 89 The crest is thick enough to be divided into three lips; inner, middle and outer. To the inner lip the transversalis muscle is attached in the anterior three-fourths, and the quadratus lumborum and erector spina? muscles on the rest. To the middle lip the obliquus internus abdominis muscle, on the anterior two-thirds. To the anterior half of the outer lip, the obliquus externus abdominis, with the latissimus dorsi and the gluteus maximus muscles on the posterior half. Below the anterior-superior spine is a notch, which ends in the anterior-inferior spine, to which is attached the rectus femoris muscle and the ilio-femoral band of the hip-joint. Below this spine is a broad shallow groove over which the tendon of the ilio-psoas muscle passes on its way to its insertion on the femur. On the internal surface of the ilium is a fossa, the iliac fossa, giving attachment to the iliacus muscle. Behind this is an articular surface, corresponding to the same-shaped surface on the sacrum, the auricular surface, for articulation with each other. A rough surface above this provides for the posterior ligaments of the joint. The iliac fossa is bounded below by a slight ridge, called the il io- pectinal line, which marks the top of the true pelvis. To this line is attached the pectineus muscle. The posterior surface or dorsum of the ilium presents three lines, the superior, middle and inferior gluteal lines. Above the supe- rior line is the gluteus maximus muscle; between the superior and middle lines is attached the gluteus medius muscle; between the middle and inferior lines is the gluteus minimus muscle. Between the inferior line and the edge of the acetabulum is the attachment of the reflected tendon of the rectus femoris muscle. Below the posterior-inferior spine, on the ventral surface is the space occupied by the pyriformis. The Ischium.-The ischium is the lower and posterior part of the hip-bone, and forms about two-fifths of the acetabulum. It pre- sents a heavy thick tuberosity, a ramus, and a spine. The tuber- osity is at the lowest part and supports the weight of the body when sitting in a correct position. It gives attachment to the semi- membranosus, the semitendinosus, the biceps femoris, the adductor magnus, the gemellus inferior and the quadratus femoris muscles. From the tuberosity the ramus ascends to join the ramus of the os pubis, anteriorly. To it is attached the adductor magnus, the obtu- rator externus and the obturator internus muscles. On the front wall of the true pelvis is a large foramen, the obturator or thyroid foramen, which in life is covered by the obturator membrane. From this and the edges around on the inner surface arises the obturator internus muscle. Above the tuberosity, posteriorly, is the spine, with a small notch (lesser sacro-sciatic) below and a large notch (greater sacro-sciatic) above. To the spine is attached the gemellus superior. 90 THE OSSEOUS SYSTEM Fig. 76.-The right hip-bone, outer surface. (Testut.) Fig. 77.-Areas of muscular attachment, outer surface of right hip-bone. (Testut.) THE BONES OF THE LOWER EXTREMITY 91 Fig. 78.-The right hip-bone, inner surface. (Testut.) Fig. 79.-Areas of muscular attachment, inner surface of right hip-bone. (Testut.) 92 THE OSSEOUS SYSTEM The Os Pubis.- The os pubis forms the anterior part of the true pelvis, and is composed of three parts, the body, the horizontal and the descending rami. The body is quadrilateral and in the lower front part gives attachment to the adductors longus, brevis and gracilis, and a part of the magnus muscles. On its upper border is the spine to which Poupart's ligament and the outer pillar of the external abdominal ring are attached. Along the upper border, internal to the spine is the crest, to which is attached the rectus abdominis, the pyramidalis muscles and the conjoined tendon of the obliquus internus and transversalis muscles. On the inner side of the body is a rough articular surface for its articulation with the fellow of the opposite side. The descending ramus joins the ramus of the ischium and gives attachment to the adductor magnus muscle. The horizontal ramus extends outward from the body to the ilium, and forms a fifth of the cavity of the acetabulum. Fig. 80.-The planes of the pelvis. (Testut.) The Pelvis.-The cavity of the pelvis is shallow in front and deeper behind. The opening at the top is called the inlet, while that below is the outlet. In the erect position of the body the pelvis is tilted so the plane of the inlet is at an angle of from 50 to 60 degrees with the horizontal, and that of the outlet at an angle of about 15 degrees. The weight of the body is transmitted from the sacro-iliac synchon- drosis to the acetabulum when in a standing position and to the tuberosities of the ischium when in a sitting position. To thus receive and transmit the weight there are very strong ridges of THE BONES OF THE LOWER EXTREMITY 93 bone between these parts of the hip-bone, these ridges being strength- ened and connected together anteriorly by counter arches which meet at the symphysis pubis. The expanded upper part of the pelvic girdle helps to support the abdominal viscera and furnishes attachment to many muscles forming the abdominal wall. The large surface, external and internal, gives opportunity for many muscles, with admirable leverage, to connect the trunk and lower extremities. The bones of the true pelvis contain and protect the pelvic viscera, and these are in intimate relation with those of the abdomen. The true pelvis in the two sexes differs in size and form. In the female the bones are smoother and lighter, as the muscles are usually exercised less vigorously. The cavity is broader, more Fig. 81.-The female pelvis, rear view. (Testut.) capacious and less deep. About puberty, the female characteristics become marked, but prior to that the pelvis is undifferentiated, and the narrow and deep male type prevails. It is noticeable that the "athletic woman" is narrow in the hips and pelvis, retaining the characteristics of the pre-pubertal pelvis. The Femur.-The femur, the longest bone of the body extends between the hip-bone and the tibia and articulates with both. It has a shaft and two extremities. The upper extremity presents a head, neck and two trochanters, great and small. The head, which articulates with the acetabulum, is covered with cartilage in the recent state, and in shape is more than a hemi- sphere. Below and behind the center is a small depression for the ligamentum teres, which holds it to the acetabulum. The neck 94 THE OSSEOUS SYSTEM Fig. 82.-The right femur, front view. (Testut.) Fig. 83.-Areas of muscular attach- ment, ventral surface of right femur. (Gerrish.) joins the head to the shaft, and is directed outward, downward and slightly backward, forming an angle of about 125 degrees with the shaft. At the junction of the neck and shaft are two projections, a large one externally, the great trochanter; and a small one, the THE BONES OF THE LOWER EXTREMITY 95 Fig. 84.-The right femur, rear view. (Testut.) Fig. 85.-Areas of muscular attach- ment, dorsal aspect of right femur. (Gerrish.) small trochanter, pyramidal in shape which presents from the inner and dorsal aspects. The great trochanter is a heavy quadrilateral process continuous with the outer surface of the shaft, and whose upper surface is on a 96 THE OSSEOUS SYSTEM level with the highest part of the neck, locating the hip-joint. From the top of the great trochanter to the small one, run rough lines, that on the front, the anterior intertrochanteric, that on the back the posterior intertrochanteric lines. The anterior line limits the neck in front and gives attachment to the capsular ligament. This line is continued around the bone as the spiral line, and joins the tinea aspera. The vastus internus muscle is attached to it. On the back of the trochanter is a rough vertical line, the gluteal ridge, to which the gluteus maximus muscle is attached. The quadratus femoris muscle is inserted near by. Externally on the trochanter are the attachments of the gluteus medius and minimus and the vastus externus muscles. Just internal to the upper part of the trochanter is a deep fossa into which the finger fits snugly, and so named the digital fossa, on the floor of which is the insertion of the obturator externus muscles. Above and in front the gemelli, the obturator internus, and the pyriformis muscles are attached. The small trochanter receives the tendon of the ilio-psoas muscle. The shaft of the femur is nearly cylindrical, but with a flattened front and a prominent ridge behind, the linea aspera. It increases in size at the lower end. The front and sides of the shaft give attachment to the three vasti muscles, the internus, externus and intermedius. The linea aspera formed by the joining of the spiral line and the gluteal ridge is thick and heavy in the middle third, and then divides into the internal and external condylar ridges, by which it continues to the condyles. The area enclosed by these ridges is the upper part of the popliteal space. To the linea aspera are attached the adductors magnus, longus and brevis, the pectineus, the short head of the biceps femoris, the vasti externus and internus muscles. The lower extremity of the femur is much expanded, and has two large condyles, internal and external. Behind they are separated by the intercondyloid notch, but in front the trochlear surface for the patella unites them. If the femur is held vertically, the internal condyle is apparently longer, but with the bone in position as in life, the lower edges are in line with each other and with the articular surface of the tibia. On the lateral surface of each condyle is a rough prominence, the tuberosity, which gives attachment to the ligaments of the knee-joint. Above the posterior aspects of the condyles the two heads of the gastrocnemius muscle are attached; from the outer tuberosity the popliteus muscle and above that, the plantaris muscle. The Patella.-The patella on the front of the knee-joint is a small, flattish, sesamoid bone, with an articular surface dorsally and a rougher surface anteriorly. It articulates with the trochlear surface THE BONES OF THE LOWER EXTREMITY 97 of the femur and takes part in the complicated knee-joint. Anato- mists differ as to whether it should be considered as contained within the tendon of the quadriceps extensor cruris muscle or as giving insertion to it. Fig. 86.-The right patella, ventral surface. (Testut.) Fig. 87.-The right patella, dorsal surface. (Testut.) The Tibia.-The tibia is the larger and heavier of the two bones of the leg, and presents a shaft and two extremities, the upper of which takes part in the knee-joint, and the lower in that of the ankle-joint. The upper extremity is thick and heavy with a tuberosity on each side. On the upper articular surface of these are depressions for the reception of the condyles of the femur. Project- ing upward between these depressions is a spine, with a double peak, and behind this is a notch, the popliteal notch. With the area immediately below this, and that on the lower part of the femur, the diamond-shaped popliteal space is formed The lower part of the tuberosities in front is marked by a promi- nent elevation, the tubercle of the tibia, to which the tendon of the quadriceps extensor cruris muscle is attached. The body rests upon the tubercle in kneeling. On the outer tuberosity, a little to the rear is an articular surface for the head of the fibula. On the inner tuberosity is seen a groove in which the tendon of the semimembranosus muscle is inserted. The shaft of the tibia gradually tapers from the tuberosities down- ward, and is again expanded at the lower end. Just below the inner tuberosity on the lateral aspect of the shaft is the common attach- ment of the sartorius, gracilis and semitendinosus muscles. The internal surface, below these muscular attachments is sub- cutaneous. The external surface presents a grooved area for the attachment of the tibialis anterior muscle on the upper two-thirds. On the posterior surface, from the articular facet for the head of the fibula, an oblique line passes downward and inward to nearly the middle of the shaft. This gives attachment to the soleus muscle and on the triangular surface above, to the popliteus muscle. 98 THE OSSEOUS SYSTEM Below this line the space is divided between the tibialis posterior muscle on the outer side and the flexor longus digitorum muscle on the inner side. Fig. 88.-The right tibia and fibula in their normal relations, front view. (Modi- fied from Testut.) Fig. 89.-Areas of muscular attach- ment, anterior aspect of the tibia and fibula. (Gerrish.) Of the borders, the external gives attachment to the interosseous membrane, and the anterior is noticeable for its sharp edge, "the shin," subcutaneous and serving as a sensitive outpost. The lower extremity of the tibia is expanded on the inner aspect into the internal malleolus, which enters into the formation of the ankle- THE BONES OF THE LOWER EXTREMITY 99 joint. On the opposite side is the surface for articulation with the fibula. On the under surface is a broad area for articulation with the astragalus. Grooves for the passage of tendons are seen on the back. Fig. 90.-The right tibia and fibula in their normal relations, rear view. (Tes- tut.) Fig. 91.-Areas of muscular attach- ment, posterior aspect of the tibia and fibula. (Gerrish.) The Fibula.-The fibula or the outer bone of the leg is very slender, with the surfaces changing in direction so frequently it is very diffi- 100 THE OSSEOUS SYSTEM cult to distinguish and describe borders or surfaces. The upper extremity or head has a conical process above, the styloid process, to which the tendon of the biceps femoris muscle is attached. A facet provides for the articulation with the tibia. The shaft gives attachment to the anterior group of muscles that flex the foot, namely, extensor longus digitorum, proprius hallucis and peroneus tertius; the external or foot pronator group, peroneus longus and brevis; the posterior or foot extensor group, flexor longus hallucis and soleus; and the supinator muscle, tibialis posterior. The lower extremity presents the external malleolus, a process that extends downward beyond that on the inner side, to take part in the ankle- joint. A facet on the inner side articulates with the tibia and another, somewhat to the front, with the astragalus. Fig. 92.-Horizontal section of the bones of the leg at the junction of the upper and middle thirds, showing their borders and surfaces and the relations of the inter- osseous membrane. (Testut.) The Bones of the Foot.-The bones of the foot have an arrangement similar to that in the hand, but with certain essential differences due to the differences in function. While the hand is a prehensile organ, the foot is an organ for support and locomotion. Seven tarsal, five metatarsal and fourteen phalanges make up the total. The description of the tarsal bones follows. The Astragalus .-The astragalus unites with the tibia and fibula to form the ankle-joint. It is joined to the calcaneum behind and to the scaphoid in front. The weight of the body is transmitted to the astragalus through the tibia, so the bone is of necessity strong and heavily built. The Calcaneum.-The calcaneum or heel bone is the largest of the tarsal bones and transmits the weight of the body to the ground. The hind part of the bone is placed lower than the front, and on the posterior surface gives attachment to the tendo Achillis, the com- bined tendon of the gastrocnemius, soleus and plantaris muscles. Jutting out from the inner side is a shelf-like process the susten- taculum tali, on which the astragalus rests in its articulation with THE BONES OF THE LOWER EXTREMITY 101 the calcaneum. On the anterior aspect is a facet for articulation with the cuboid. The Cuboid.-The cuboid is in front of the calcaneum and on the outer side of the foot. It articulates with the fourth and fifth metatarsals, as well as with the calcaneum. On the under surface is a deep groove through which passes the tendon of the peroneus longus muscle. Fig. 93.-Right astragalus, under surface. (Spalteholz.) Fig. 94.-Right calcaneum, internal surface. (Spalteholz.) The Scaphoid.-The scaphoid is placed on the inner side in front of the astragalus with which it articulates, as well as with the cuboid, the internal, middle and external cuneiforms. It has a tubercle on the inner surface which serves to locate the medio-tarsal-joint and gives attachment to the tibialis posterior muscle. 102 THE OSSEOUS SYSTEM Fig. 95.-The bones of the right foot, viewed from above. (Albinus.) THE BONES OF THE LOWER EXTREMITY 103 Fig. 96.-Areas of muscular attachment on the dorsal surface of the bones of the foot. Where the areas of origin and insertion are both presented they are in the same color. The third dorsal interosseous is not labeled. P.I., plantar interosseous insertion; INS., insertion. (Gerrish.) 104 THE OSSEOUS SYSTEM Fig. 97.-The bones of the right foot, viewed from below. (Spalteholz.) THE BONES OF THE LOWER EXTREMITY 105 Fig. 98.-Areas of muscular attachment on the plantar surface of the bones of the foot. Where the areas of origin and insertion are both presented they are in the same color. OR., origin; INS., insertion. The insertion of the second and third tendons of the flexor brevis digitorum are not labeled. (Gerrish.) 106 THE OSSEOUS SYSTEM The Cuneiform Banes.-Three cuneiform bones in front of the scaphoid are wedge-shaped and articulate with each other, with the scaphoid, the cuboid and all the metatarsals except the fifth. Fig. 99.-The bones of the right foot, viewed from the outer side. (Testut.) The Metatarsal Bones.- The five metatarsal bones articulate with the front row of the tarsus and with the first phalanx of the corresponding toes. That of the great toe is much heavier than the others, and the fifth or the metatarsal of the little toe is the longest, with a prominent tubercle at its upper end. Fig. 100.-The bones of the right foot, viewed from the inner side. (Spalteholz.) The Phalanges.-The phalanges, two for the great toe and three for all the others are similar to those of the hand, but much shorter, especially the terminal or ungual phalanges. Many muscles find attachment to the bones of the foot. See Figs. 96-98. The Foot as a Whole.-The bones of the foot form two arches, one longitudinal, the other transverse. When the two feet are placed side by side, the structure is a dome, which is architecturally the strongest form of support possible for the weight of the body. The bones concerned in the long arch are the astragalus as the THE BONES OF THE LOWER EXTREMITY 107 keystone, the calcaneum as the posterior division, the scaphoid, three cuneiform, and first three metatarsals as the anterior division. The outer part of the foot, the cuboid and two outer metatarsals serve as a buttress to the arch. The transverse arch has its inner pier at the internal cuneiform and the first metatarsal; the outer pier at the cuboid and the fifth metatarsal. This arrangement of the bones provides protection for the muscles and nerves in the sole of the foot, adds to the spring in walking and lessens jar in falling upon the feet as well as increasing their beauty. While the weight of the body ordinarily rests upon the heel, we tread upon the front part of the foot. In normal barefoot walking the front of the foot touches the ground before the heel does, but this is not the case when shoes with heels are worn. QUESTIONS. How many bones to form the cranium? Why should there be that many? Name the parts of a typical vertebra. How are the cervical vertebrae distinguished? How are the thoracic vertebrae distinguished? Describe a typical rib. Name the parts of the scapula. Distinguish the right humerus, and place it so it will correspond with its position in the body. What are the markings on the radius? How many carpal bones are there? Why should there be so many bones in a hand? What and where is the patella? How is the femur directed when articulated? Name the principal points of interest on the ilium. What is the "linea as per a?" What is the tubercle of the tibia, and what is attached thereto? What is the "arch of the foot?" CHAPTER IV. THE ARTICULATIONS. The bones of the skeleton are held together in place by articula- tions or joints, which have certain common characteristics. In a typical joint, the expanded ends of two bones are covered with hyaline cartilage in a thin layer, with greater thickness where the pressure is greater. This cartilage makes for smoothness, lack of friction, and elasticity. There may be rings or plates of fibro- cartilage around or between bones to deepen sockets or to secure better adaptation of surfaces or increase the buffer action. A continuous sheath of white fibrous tissue covers in the joint, holding the bones together, with accessory bands where the strain is greater. The white fibrous tissue while flexible is inextensible, so there is no danger of the bones separating farther than for the normal range of movement. Inside the fibrous sheath is a lining of epithelial tissue, which secretes a glairy material similar in appearance to the white of an egg, called synovia. This is to lubricate the joint. In addition, small sacs, or bursa?, are frequently present to provide lubrication to structures around the joint (periarticular). Classes of Joints.-Such a joint as that described above allows a more or less free range of movement, and is classed as diarthrodial. Several subdivisions of this class are made, to be described later. Some joints are made by two bones in contact without the cover- ing of cartilage, as in the sutures of the skull, where a layer of fibrous material holds them together. Or, there may be a socket of bone, into which a cone of cartilage fits, and is held by the perichondrium and the periosteum, as in the articulation of the ribs with their cartilages. Such joints permit no motion and are called synarthrodial. Another class have a plate of fibrocartilage between the bones which is firmly attached to both, as in the symphysis pnbis, and in the articulations between the bodies of the vertebrae. These joints have a small amount of motion and are called amphiarthrodial. The diarthrodial joints are divided into several classes according to the kind of motion permitted. This is dependent upon the shape of the articulating surfaces, but the ligaments connecting the bones and the muscles surrounding limit the motion. When a movement takes place about a transverse axis, giving a 108 THE ARTICULATIONS OF THE VERTEBRAL COLUMN 109 change in the extent of the angle between the bones, it is called flexion if the angle is reduced, and extension if the angle is increased. If an angular movement toward the middle line of the body, the middle of the second finger or the second toe occurs, it is called adduction. If the movement is away from these centers, the move- ment is abduction. A combination of the above four movements in one continuous movement is circumduction, with the figure of a cone described in space, the apex at the joint and the base of the cone at the further extremity. This should not be confounded with rotation. Rotation is the movement of a bone around a longitudinal axis, in which the figure described in space is a cylinder. Gliding is a sliding of surfaces upon each other without any angular or rotary movement. Classes of Diarthrodia.-Arthrodia or gliding joints allow a limited gliding between two nearly flat surfaces, as those of the articular processes of the vertebrae. Ginglymus or hinge joints allow movements of flexion and exten- sion about a transverse axis, as in the elbow- and knee-joints. Condyloid joints allow abduction, adduction, flexion, extension and circumduction, but not rotation, as the surfaces of bone forming the joint are oblong and spheroidal in form. The metacarpo- phalangeal joints illustrate this kind of joint. Reciprocal Reception.-A modification of condyloid joints, called either "saddle joints" or those of reciprocal reception have the surfaces reciprocally saddle-shaped, as in the carpo-metacarpal joint of the thumb. They allow all movements except rotation. Ball-and-socket joints, such as those at the hip and shoulder consist of a more or less spherical head received into a cup-shaped cavity. They allow free movement in every direction. Pivot joints, those between a pivot and encircling ring, as in the articulation between the axis and atlas, and that between the upper parts of the radius and ulna, allow the movement of rotation only. In describing the articulations, those not of particular interest to the student of hygiene will be given but brief consideration. THE ARTICULATIONS OF THE VERTEBRAL COLUMN. These include the joints between the bodies of the vertebrae, the articular processes, the laminae, the spinous processes and the trans- verse processes. The bodies of the vertebrae are joined together by disks of fibro- cartilage, which correspond in shape with the bodies. These disks are tough, elastic and compressible, varying in thickness in different regions of the spine. In the center of the disk is a spherical mass of pulpy material, which is compressed by the layers of fibrocartilage, 110 THE ARTICULATIONS so it rebounds when the mass is cut across, and seems like a small ball or pivot. Around this mass, the vertebrae move in every direc- tion. The thickness of these disks varies, being thinnest in the cervical, and thickest in the lumbar region of the spine. Passing down the front of the bodies and intervertebral disks is the anterior common ligament, beginning at the under surface of the occiput, as a narrow band, and widening as it descends until it reaches the sacrum. This ligament connects the front of the bodies of the vertebrae and limits the movement of extension. The posterior common ligament passes along the posterior sur- faces of the bodies and disks, from the occiput to the coccyx, being broader above and narrower below. It connects the backs of the bodies, helps to form the lining of the vertebral canal, and limits flexion of the spine. Fig. 101.-Two lumbar vertebrae in sagittal section. (Testut.) These intervertebral articulations are amphiarthrodial joints, allowing slight movement in every direction with the fibrocartilages compressed when the rest of the spinal articulations are in movement. The joints between the articular processes are gliding joints, having capsular ligaments lined with synovial membrane. These ligaments are loosest in the cervical region and tightest in the thoracic. Connecting the laminae are ligaments that are unusual in that they contain elastic fibrous tissue. These are the lig amenta sub- flava, and besides causing the return of the surfaces to their normal position after each movement, they prevent the capsular ligaments from being pinched between the articular surfaces during such movement of the spine. The tips of the spinous processes are con- nected by bands of fibers, called the supraspinous ligaments. In the cervical region, these are accentuated as the ligamentum nuchae, THE ARTICULATIONS OF THE VERTEBRAL COLUMN 111 or nape ligament. In quadrupeds this is very strong, as it supports the head, but it is much less marked in man, and has some elastic fibers. It gives attachment to several muscles. Ligaments pass from the under surface of one spine to the upper border of the spine below, and between the transverse processes. The spinal column is the axis of the skeleton, and every move- ment of the body influences its position, and the pull of the muscles acting upon it. Further, it must resist jar and provide strength with mobility. The motion between any two vertebrae is slight, but the sum of the movements of the twenty-six vertebrae amounts Fig. 102.-The ligamentum nuchse, seen from the right side. (Henle.) to a relatively large range. Around the pulpy ball in the center of the intervertebral fibrocartilage, the movement is in every direction, as of a ball-and-socket joint, but limited by the articular processes and the ligaments. Noting the direction in which the articular processes face, and remembering that gliding is their only possible movement, it is seen that in the cervical region the obliquity of the surfaces would allow some movement in practically all directions. In the dorsal region, side bending would be more possible and in the lumbar spine the movements of flexion and extension would take place most readily. The overlapping spines in the thoracic region limit extension 112 THE ARTICULATIONS while the attached ribs prevent much movement laterally. The thick intervertebral disks in the lumbar region provide for fairly free movement, and the small bodies in the cervical region allow a similar freedom there. The spine is a flexible structure, already curved in two directions in the antero-posterior plane, and as Lovett has so well pointed out it must be considered as a flexible curved rod, and cannot be bent laterally without accompanying torsion. ARTICULATIONS IN THE UPPER CERVICAL REGION. The condyles of the occiput articulate with the facets on the upper surface of the atlas, forming a condylar joint. Flexion, extension and side bending, but not rotation is possible. The articulation between the odontoid process of the axis, and the atlas provides for free rotation, and the movements of the head on the atlas and of the atlas on the axis are usually closely associated and merged, amounting to a very free range, a:s though it were a ball-and-socket joint. Fig. 103.-Diagram of the displacement of the ribs and sternum in inspiration: a, indicates the degree of upward movement; b, that of forward movement. (Testut.) ARTICULATIONS OF THE THORAX. The anterior ends of the first seven ribs articulate with the facets on the sternum, and allow a slight hinge movement on the sagittal and obliquely vertical axis. The cartilages of the next three ribs are joined to that of the seventh and thus indirectly to the sternum. THE ARTICULATIONS' OF THE UPPER EXTREMITY 113 Posteriorly, the heads of the ribs articulate with either the body of the corresponding thoracic vertebra, or with the bodies of two adjoining vertebrae and the intervertebral fibrocartilage. The tubercles of the ribs articulate with the facets on the transverse processes of the vertebrae. Capsular ligaments hold the bones together. The movement at these joints is mostly rotation around an oblique axis upward or downward. The ribs are inclined obliquely downward, and during the movement of inspiration, the inclination is lessened as the sternal ends of the ribs move forward-upward. This increases the sagittal diameter of the thorax. At the same time, the lateral diameter is increased by the lessening of the angle with the costal cartilages, in front, and by the elevation of the lateral part of the rib and the eversion of the lower border, behind. The upper ribs, first and second, being flatter and with less obliquity are raised in inspiration, so increasing the vertical diameter of the thorax. During expiration, the reverse action takes place by the relaxation of the muscles. THE ARTICULATIONS OF THE UPPER EXTREMITY. The upper extremity is attached to the main skeleton at only one place, the articulation between the clavicle and the sternum. Fig. 104.-Sterno-costo-clavicular articulation, front view. The left half is seen in coronal section. (Testut.) The Stemo-clavicular Articulation.-In the sterno-clavicular articu- lation the two surfaces of bone, the facet on the manubrium and the end of the clavicle do not fit accurately together, so there is a plate of fibro-cartilage interposed, with synovial cavities on each 114 THE ARTICULATIONS side of it. The surfaces glide upon each other as a rounded head in a shallow socket. This, while giving freedom, makes for easy displacement. To prevent upward displacement, a strong band of fibers, the interclavicular ligament, passes from the end of one clavicle to that of the other and dips down to the upper border of the sternum. Anterior and posterior sterno-clavicular bands guard the joint front and back, and additional fibers complete a capsule. An accessory band of fibers, the costo-clavicular or rhomboid liga- ment, joins the lower surface of the clavicle to the front of the first rib. This aids in preventing upward displacement, as well as that in the backward direction. The student should place one finger on the articulation and note the movements of the clavicle when raising and lowering and carrying the arm forward and backward. The clavicle with the scapula moves up and down, backward and forward and in circumduction. On raising the arm a slight rotation occurs. Fig. 105.-Glenoid fossa of right side. (Testut.) The Scapulo-clavicular Articulation.-The scapula is joined to the clavicle by a gliding joint between the acromial end of the clavicle and the acromion of the scapula. The capsular ligament surround- ing it, allows only a small amount of movement. A much stronger union is made between the coracoid process of the scapula and the under surface of the clavicle. From the root of the coracoid process, strong bands of fibers pass to the conoid tubercle of the clavicle. This is the conoid ligament by which the scapula is said to hang from the clavicle. From the upper surface of the coracoid process the trapezoid ligament extends to the trape- zoid ridge of the clavicle. Movements of the acromio-clavicular joint are usually combined with those of the sterno-clavicular joint. The combination of turning the glenoid fossa upward or downward, THE ARTICULATIONS OF THE UPPER EXTREMITY 115 with the elevation or depression of the clavicle results in what is known as the rotation of the scapula. When the arm is raised, this rotation turns the glenoid fossa more upward and outward and carries the lower angle outward. The reverse occurs in lowering the arm. The scapula and clavicle move independently of the arm with an upward and forward movement, and a downward and backward movement. In these, the lower angle of the scapula does not move outward toward the axilla as in the movements associated with arm raising or lowering. An additional union between the clavicle and scapula is made by the coraco-acromial ligament, passing between the coracoid process and the acromion, and forming an arch over the shoulder joint. This protects the joint and holds off the deltoid muscle. Fig. 106.-Shoulder-joint, rear view. The hind part of the capsular ligament and most of the head of the humerus have been removed. (Testut.) The Shoulder-joint.-The parts concerned are the rounded head of the humerus and the glenoid fossa of the scapula. Both surfaces are covered with cartilage, and around the edge of the fossa to deepen it is a rim of fibro-cartilage, the glenoid ligament, which is triangular on cross-section. From the circumference of the fossa the capsular ligament extends to the anatomical neck of the humerus. This capsule is longer than the actual distance requires but allows great mobility in the joint. The synovial membrane lines the capsule and extends down into the bicipital canal. The capsular ligament does not hold the bones together, but as a vacuum exists within the capsule, atmospheric pressure does. Various tendons 116 THE ARTIC ULA TIONS serve to help prevent dislocation. That of the biceps muscle goes within the capsule, and to the upper border of the fossa, guarding the joint above. This is noticeable when the arm is in abduction, and the latissimus dorsi and pectoralis major muscles are pulling downward, as in hanging by the hands. Tendons of supraspinatus, infraspinatus and teres minor muscles are above and posterior; that of the triceps muscle below, the sub- scapularis muscle in front. Between these two latter, is an unpro- tected space, that allows the head of the humerus to be dislocated under violent strain. The inner surface of the front of the capsule is further strengthened by three bands, gleno-humeral, passing from the edge of the fossa to the greater tuberosity of the humerus. Fig. 107.-Shoulder-joint, front view. (Testut.) Strong bands pass from the coracoid process of the scapnla to the anatomical neck of the humerus, in close association with the capsule. The shoulder-joint is a ball-and-socket joint, allowing movement in all directions, flexion, extension, rotation, abduction, adduction and circumduction. Flexion and extension, abduction and adduc- tion are possible through 90 degrees. In abduction, the head of the humerus is prevented from going further by the greater tuberosity striking against the acromion process and the coraco-acromial liga- ment. Before the arm has gone far in these movements, the glenoid fossa begins to turn, so complete extension or abduction takes place by the combination of rotation of the scapula, and the movement at the shoulder-joint. THE ARTICULATIONS OF THE UPPER EXTREMITY 117 Inward and outward rotation occurs around an axis from the center of the head to the inner condyle of the humerus, with a range of about 90 degrees. The subacromial bursa between the capsule and the deltoid muscle is important. Fig. 108.-Elbow-joint, mesial view. (Poirier.) Fig. 109.-Elbow-joint, outer side. (Testut.) The Elbow-joint.-This is formed by the trochlear surface of the humerus and the greater sigmoid cavity of the ulna. Both surfaces are covered with cartilage, and a capsule surrounds the joint, with bands of fibers accentuating the internal, external, anterior and posterior aspects. Of these, the internal lateral bands are the strongest. The anterior fibers are attached to the brachialis muscle, 118 THE ARTICULATIONS which contracts in flexion of the elbow, and draws the capsule out of the way of being pinched by the bony margins. The triceps muscle acts similarly for the posterior fibers. The capsule is lined by synovial membrane which is continued into the fossae about the joint. This is a hinge joint, allowing flexion and extension around an oblique axis inclined at an angle of 84 degrees with the shaft of the Fig. 110.-Elbow-joint in sagittal section, showing the articular synovial sac and the bursae of the olecranon and the biceps. (Testut.) humerus. In flexion of the forearm, the hand moves toward the middle line of the body, and vice versa in extension. The head of the radius moves on the capitellum and aids in preventing side dis- placement of the bones. In the semi-flexed position of the elbow movement of the radial head in pronation and supination is most free. The tendons of the biceps, brachialis and triceps muscles do much to strengthen this joint. THE ARTICULATIONS OF THE UPPER EXTREMITY 119 The Radio-ulnar Articulations.-The radio-ulnar articulations con- sist of two joints and a fibrous union. The superior, formed by the head of the radius pivoting in the lesser sigmoid cavity of the ulna, has the orbicular ligament surrounding, and holding it as in a sling. Its movements in connection with the inferior radio-ulnar articula- tion are pronation (turning the palm downward) and supination (turning the palm upward). The fibrous union between the two bones of the forearm consists of an oblique band above and the interosseous ligament below, extending to the lower articulation. As these fibers are obliquely placed the space between the bones is greater during supination. The inferior radio-ulnar joint is formed by the head of the ulna in the sigmoid cavity of the radius. It is closely associated with the wrist-joint by the triangular fibrocartilage which connects the radius and ulna and separates the ulna from the wrist-joint. It is enclosed by a capsular ligament. The lower end of the radius moves about the ulna in rotation, carrying the hand with it. The Wrist-joint.-The wrist is a condyloid joint, formed by the lower end of the radius and the carpal bones, scaphoid and semilunar. The lower end of the ulna is separated from the joint by the triangular fibrocartilage, the lower surface of which articulates with the upper surface of the cuneiform. Bands of fibers, anterior, posterior, internal and external lateral form a capsule lined by synovial membrane. The posterior aspect of the joint is strengthened by the extensor tendons. The Carpal Articulations.-The carpal articulations consist of bands of fibrous tissue connecting the various carpal bones to each other, front, back and in between. Fibers between the carpal and metacarpal, the metacarpal and phalanges are on all sides. The phalanges are united with each other by capsular ligaments. Movements of the wrist-joint are flexion, extension, abduction, adduction and circumduction, but not rotation. The carpal bones form gliding joints with each other, and pro- vide considerable elasticity, which lessens shock. The carpo-meta- carpo joints, exclusive of the first and fifth allow flexion and exten- sion. The fifth provides for a greater amount of these movements, and the direction of the flexion is outward, so cupping the hand and causing opposition of the little finger. The joint of the metacarpal of the thumb and corresponding carpal bone is of reciprocal recep- tion, with flexion, extension, abduction, adduction and circumduc- tion. Flexion is obliquely forward and inward allowing the opposi- tion of the thumb to any of the fingers. The metacarpo-phalangeal joints are condyloid, with the usual movements, excepting that the first allows only flexion and extension. The various joints of the hand combine to allow prehension and a variety of movements characteristic of man. 120 THE ARTICULATIONS The fifth lumbar vertebra articulates with the upper surface of the sacrum, and very strong ligaments hold them together. The fibrocartilaginous disk between them is especially thick so allowing free flexion and extension, as in sitting or in rising from the sitting position. The inclination of the pelvis depends partly upon the relative position of these bones. The articulations between the sacrum and coccyx and between the segments of the coccyx allow a small amount of motion. THE PELVIC ARTICULATIONS. Fig. 111.-Articulations of the pelvis, rear view. (Testut.) The Sacro-iliac Synchondrosis.-The sacro-iliac synchondrosis is formed by the union of their two auricular surfaces, connected by very strong ligaments, especially those posterior. Under normal conditions no motion is possible between these bones. The obliquity of the pelvis is modified by the relation of these bones, also. The Symphysis Pubis.-The symphysis pubis, or joint between the two pubic bones, has a disk of fibrocartilage between, with liga- ments above, below, front and back. No movement is allowed. THE ARTICULATIONS OF THE LOWER EXTREMITY. The Hip-joint.-The hip-joint is analogous to the shoulder-joint in the upper extremity. It is formed by the rounded head of the THE ARTICULATIONS OF THE LOWER EXTREMITY 121 femur, and the acetabulum. The surfaces are prepared by the cover- ing of cartilage. Around the edge of the acetabulum is a rim of fibrocartilage, the cotyloid ligament, which deepens the cavity to better fit the head of the femur. The notch at the lower border is bridged by the transverse ligament, forming a foramen through which passes nerves and bloodvessels. Attached to the head of the femur and going to the bottom of the cavity is a band, the ligamen- tum teres, which holds the femur in the socket, even after the cap- sular ligament is removed. Coming from the rim of the acetabulum, Fig. 112.-Hip-joint in coronal section. (Testut.) beyond the cotyloid ligament is a sheath of fibrous tissue, the capsular ligament. This extends to the anterior intertrochanteric line in front, and half an inch internal to the posterior intertro- chanteric line behind. On the outside of the capsule are three accessory bands, of which the first is most important. The ilio- femoral band, or " Y" ligament of Bigelow, is shaped like an inverted "Y" with the stem attached to the anterior-inferior iliac spine, and the wide lower end to the anterior intertrochanteric line. The pubo- femoral band passes from the pubic bone to the femur. Between Fig. 113.-Hip-joint, front view. The cavity is distended artificially. (Testut.) Fig. 114.-Hip-joint, front view. The capsular ligament has been largely removed. (Testut.) THE ARTICULATIONS OF THE LOWER EXTREMITY 123 this and the iliofemoral band, the capsule is thinner and weaker, providing for dislocation. The third accessory band, the ischio-femoral passes from the ischium just below the acetabulum to the base of the great tro- chanter. The capsule is further strengthened by fibers from the tendinous sheath of various muscles. The ilio-psoas in front; the pectineus on the inner side; obturator externus behind 'and below; obturator internus, two gemelli and pyriformis behind and the rectus femoris and gluteus minimus externally. The capsule is lined by a synovial membrane, which is reflected on to the neck of the femur and sur- rounds the ligamentum teres. This ball-and-socket joint allows all movements though their extent is less than those of the shoulder- joint. Flexion and extension occur without the head of the femur leav- ing the socket. This is true for none of the other movements. Extension is limited by the "Y" ligament, which also helps to prevent the trunk falling backward. Flexion takes place to 140 degrees, until limited by the contact of the thigh with the abdominal wall, if the knee flexes at the same time. If the knee is extended, the resistance of the hamstrings stops the movement at 90 degrees. The Knee-joint.-The knee-joint is formed by the condyles of the femur, the upper surface of the tibia and the patella. To the cartilage covered surface of the tibia two disks of fibro- cartilage, somewhat horse-shoe shaped, and called semilunar car- tilages are applied to deepen the cavity. The disks are thicker on the outer edges, at which they are loosely attached to the bone by the coronary ligaments, with the transverse ligament going from one to the other in front. The bones are held together by two crucial ligaments, anterior and posterior which arise from in front of, and behind the spine of the tibia, and are inserted into the contiguous surfaces of the two condyles. The patella, a sesamoid bone in the tendon of the quad- riceps extensor cruris muscle, forms the front part of the joint, and moves up and down over the trochlear surface of the femur, in extension and flexion of the joint. Surrounding the joint are bands on all sides, which are connected by additional fibers to form a complete capsule. The tendon of the quadriceps muscle, inserted into the tubercle of the tibia and some- times called the ligamentum patellae forms the front part of the capsule. Posteriorly, oblique fibers, the ligamentum Winslowii; one internal, and two external lateral ligaments complete the cover- ing of a joint that is said to be made up of three joints fused together. A most extensive synovial membrane lines the capsule, covers the semilunar cartilages and crucial ligaments. It communicates with numerous bursae around the joint, and forms a crescentic fold Fig. 115.-Knee-joint in sagittal section. (Testut.) Fig. 116.-Knee-joint, front view. Part of the ligaments have been removed on the right side. (Testut.) THE ARTICULATIONS OF THE LOWER EXTREMITY 125 Fig. 117.-The semilunar cartilages of the right knee-joint. (Testut.) Fig. 118.-Knee-joint, outer side. The synovial sacs are artificially distended. (Poirier.) 126 7 HE ART ICU LA TIONS within the joint called the ligamentum mucosa. This projects from the front of the capsule backward and upward to the front of the intercondyloid notch. The ends of the fold form the alar ligaments. Small masses of fat help to fill the spaces between the bones and form cushions. The knee-joint has many bursae, some of which communicate with the main synovial cavity. Some of the most constant and important ones are those between the bones and the tendons passing on each side of the popliteal space; above and beneath the ligamentum patelloe; over the patella; between the inner hamstring and the head of the tibia, and over the tubercle of the tibia. Fig. 119.-Tibio-tarsal and calcaneo-astragaloid articulations, in coronal section. The synovial sacs are distended. (Testut.) The knee is a modified hinge-joint with flexion and extension around an axis that shifts forward in flexion and backward in exten- sion. On account of the shallowness of the cavities on the upper surface of the tibia and the curves of the condyles, the surfaces cannot remain in constant close contact. During flexion, the crucial ligaments become tense, and pull the tibia backward, making the points of contact between the bones more to the front. By this means, relaxation of the ligaments follows, and the movement is allowed to continue. The flexor muscles of the joint tend to pull the tibia back, but this is opposed by the posterior crucial ligament, THE ARTICULATIONS OF THE LOWER EXTREMITY 127 while the anterior crucial opposes the opposite pull of the quad- riceps muscle toward the front. At the end of the movement of extension, there is a slight outward rotation of the leg, shown by the outward pointing of the foot. This is reversed at the beginning of flexion. In descending a slope, the foot naturally turns out, and vice versa. The tendons of the quadriceps, the hamstrings, inner and outer, the gastrocnemius and the popliteus muscles serve as supplementary ligaments to protect this joint. They are so adjusted that over-extension of the joint is resisted by them, enabling the body to maintain the erect position with little muscular effort. The Articulations of the Tibia and Fibula.-The articulations of the tibia and fibula are in three parts, upper, lower and middle. Bands of fibers passing from bone to bone join the head of the fibula to the facet on the outer tuberosity of the tibia. An interosseous membrane connects them throughout their length. The oblique direction of these fibers allows a slight gliding of the bones on each other, so that during flexion of the ankle there is a widening of the mortise part of the mortise and tenon of the ankle. The lower articulation merits a careful consideration. This is the ankle-joint, formed by the internal and external malleoli and the astragalus. The lower ends of the tibia and fibula form a mortise into which the astragalus fits as a tenon, giving a very strong structure to prevent lateral displacement and resist the tremendous leverage exerted by the height and weight of the body. The joint is closed in by a capsule, with ligaments on all four aspects, especially lateral. The anterior fibers pass from the front of the tibia to the upper part of the astragalus; the posterior fibers from the back in the same way. The external lateral is divided into three fasciculi, anterior, middle and posterior. The anterior bundle passes from the front of the external malleolus to the front of the astragalus; the middle bundle from the tip of the external malleolus to the os calcis; the posterior from the back of the malleolus to the outer surface of the astragalus. The internal lateral or deltoid ligament is triangular in shape attached by its apex to the tip of the internal malleolus, with its base inserted on the inner surface of the astragalus, the sustentaculum tali of the calcaneum, the scaphoid and to the infe- rior calcaneo-navicular ligament. The tendons of the muscles that move the ankle-joint, the tarsal joints and the toes are in close relation to this joint, and act as supplementary ligaments. Bursae lie between the skin and the two malleoli. A hinge movement is permitted in the ankle-joint, to less than 90 degrees. The axis of this movement is slightly oblique, and so helps to secure a stable equilibrium in standing. The movements of the ankle-joint are closely associated with those of the medio- 128 THE ARTICULATIONS tarsal articulation and the combined action of the muscles acting on both has much to do with maintaining the balance in both standing and walking. Fig. 120.-Tibio-tarsal articulation, outer side. The cavity is artificially distended. (Testut.) The Tarsal Articulations.-As in the carpal joints, the various bones of the foot are held together to form gliding joints which allow a small amount of motion, but provide for elasticity and shock absorption. The articulation of the astragalus with the calcaneum and the scaphoid, and of the cuboid with the calcaneum should receive attention. Posteriorly and externally the first two are joined by bands of fibers, and on the anterior and inner aspect the THE ARTICULATIONS OF THE LOWER EXTREMITY 129 Fig. 121. - Medio-tarsal joint, viewed from above, the astragalus having been removed. (Testut.) Fig. 122.-The plantar ligaments. (Testut.) 130 THE ARTICULATIONS calcaneum, astragalus and scaphoid are united. Between the cal- caneum and the scaphoid are the inferior and superior calcaneo- scaphoid ligaments which are partly cartilaginous (hence elastic) giving support to the head of the astragalus which rests upon them. The calcaneo-cuboid articulation on the outer side of the foot, with the astragalo-scaphoid union, forms a joint right across the foot, separating the front from the hind part and is called the medio- tarsal articulation. The bones are connected on the dorsal surface, and on the plantar surface are two ligaments, the plantar ligaments, which form the inferior calcaneo-cuboid ligament. The long and short plantar ligaments connect the under surface of the calcaneum with the under surface of the cuboid, and have much to do in main- taining the normal arches of the foot. The movements at the calcaneo-astragaloid joint are inversion, eversion, adduction and abduction. These also occur in the medio- tarsal joint as well as flexion and extension. Flexion at the medio-tarsal is associated with extension at the ankle, and the reverse. The joint between the astragalus and scap- hoid is a ball-and-socket, but its motion is limited by its association with the condyloid joint between the calcaneum and cuboid. In the medio-tarsal joint, flexion of the foot is combined with inversion of the sole and adduction of the front of the foot. If this position is exaggerated and permanent, the condition of "club foot" results. If the reverse obtains, or extension with eversion of the sole and abduction of the front, the "flat foot" or "pronated foot" is produced. The three cuneiform bones are united to all the bones in contact with them, and produce gliding joints. In the tarso-metatarsal joints, slight flexion, extension, abduction and adduction, obtain with greater freedom in these movements between the metatarso- phalangeal joints. Abduction and adduction take place from and toward the middle of the second toe. The interphalangeal joints allow flexion and extension, only. The mechanism of the foot is designed for standing and locomotion. The balanced action of the various muscles acting upon the ankle and bones of the foot, should hold it in a position in which the ligaments are not strained, but in which the long and transverse arches operate to insure elasticity and strength. QUESTIONS. Describe a typical joint. What movements are possible in joints? How much movement is possible in the spinal column, and in what direction? What articulations provide for the movements of the head? Describe the shoulder-joint. 131 THE ARTICULATIONS OF THE LOWER EXTREMITY What joints provide for pronation and supination of the hand? What relation has the strength of the ligaments of the sacro-iliac synchon- drosis to the maintenance of the erect position? Compare the structure and movements of the hip- and shoulder-joints. What are the "semilunar cartilages?" What are the crucial ligaments? How many joints are combined in the knee-joint? Describe the ankle-joint.. What movements of the foot take place at the tarsal and medio-tarsal joints? What are the articulations of the thorax, and how are the movements related to respiration? CHAPTER V. THE MUSCULAR SYSTEM. The skeletal muscles almost completely envelope the framework of the body, cover the abdominal cavity, separate the thoracic from the abdominal cavities, and are connected with the oral cavity, the nose, ear and throat. Two-fifths of the weight of the body consists of the voluntary muscular system. The size and shape of muscles varies according to their work, being broad and thin to cover cavities, and longer and narrower when moving such parts as the extremities. The muscles are covered by sheaths of fibrous tissue, called fasciae. This is divided into the superficial and deep layers, accord- ing to location. The superficial layer is directly under the skin, while the deeper layer covers the muscles, dipping down between them, and forming so-called intermuscular septa. This deep fascia holds the muscles together, and aids them in their work of coordina- tion. It frequently gives a definite area of attachment to the muscles. The relation of the fascia to the veins that drain the extremities will be considered a little later in connection with the circulation. Muscles are composed of bundles of fibers, reddish in color, each surrounded by a sheath of fibrous tissue. This sheath extends beyond the fiber, and the aggregation of extensions forms a tendon of attachment to a bone, cartilage or fascia. The fleshy portion of a muscle is called the "belly," and it is the active part. The tendinous portion is inactive, and transmits passively the pull developed by the contraction of the fleshy portion. Every fiber has its own nerve supply, with the minute nerve fibers uniting into a bundle which is between the bundles of muscle fibers. In some muscles, as the rectus abdominis, tendinous inscriptions, so-called, pass across the belly, adding to their strength. The ten- dons vary in shape from long cords to thin and broad sheets called aponeuroses, having in general a similarity to the form of the muscles of which they are a part. The various movements of the body are caused by the contrac- tion of muscles. As a muscle contracts it becomes shorter and broader. The tendons being inextensible do not change in shape, but transmit the pull to the structures to which they are attached, as bone, fascia, etc. These are moved toward each other, though one end is usually moved less than the other. 132 THE MUSCULAR SYSTEM 133 It is customary to speak of the fixed end as the origin and of the moving end as the insertion, but while this is convenient it is not always true to fact, as the conditions are frequently reversed. These terms are also used to indicate the proximal and distal ends of the muscle, the origin being that attachment nearest the center of the body or nearest the head, and the insertion that more distant. The point of application of power is also called the insertion. The application of the power of muscles should be considered from the standpoint of mechanics. The bones and muscles constitute a series of levers. Briefly a lever is a means of applying power to obtain movement more or less economically. If one wants to move a heavy stone, and is unable to lift it in his arms, a lever can be arranged that makes it easy to accomplish. By inserting the end of a bar under the edge of the stone and pressing down upon the further end of the bar, the stone is easily moved. The leverage of the bar increases the power of the individual many fold. The saying of Archimedes becomes comprehensible, i. e., "Give me a place upon which to stand and a long enough lever, and I will move the earth." Levers are divided into three classes, according to the relative position of the weight to be moved, the power to move it and its point of appli- cation, and the fulcrum about which it is moved. Let F represent the fulcrum; W the weight and P the power, and the lever in which F is in the middle is of the first class. That in which the weight is in the middle is of the second class, and that in which the power is in the middle is of the third class. The following diagram will make this clear. LEVER OF THE FIRST CLASS LEVER OF THE SECOND CLASS LEVER OF THE THIRD CLASS The majority of the muscles of the body belong to the third class of levers. This is rather wasteful of power, but there are compen- sating advantages that more than make up for this. Greater speed of movement is obtained, more beauty of form, greater convenience in use and increased security of joints. Muscles passing over more than one joint are said to have a primary action on the first joint, a secondary action on the next, and a tertiary action on the third if the contraction continues. For instance, the flexor of the fingers that is inserted in the base 134 THE MUSCULAR SYSTEM of the last phalanx of the finger, has a primary action on the joint next above; a secondary action on that further up and a tertiary action on the metacarpo-phalangeal joint. The usual action of a muscle from a fixed origin to a movable insertion is called its direct action, but when a fixed insertion acts upon a movable origin, the action is called its reversed action. THE NAMING OF MUSCLES. There are various considerations entering into the nomenclature of muscles, as action, shape, location, relative size, attachments, direction of fibers, etc. For instance, pronator teres indicates both the action as a pronator of the forearm and its round shape as distinguished from the quadratus ox square pronator. The pec- toralis major indicates the location on the chest wall, and the greater size of this muscle as compared with the minor pectoral. The brachio-radialis indicates the bones to which the muscle is attached, the obliquus externus abdominis indicates the oblique direction of the fibers, as well as its external position on the abdom- inal wall, as compared with the interior position of the obliquus intemus abdominis. Attention to these names and their meanings will help to fix the actions of the various muscles in the memory. All muscles are given Latin names, as making them intelligible to scientific students everywhere. MOVEMENTS OF MUSCLES. The movements produced by muscles always involve several acting together, with still others holding the points of origin firm and others controlling the speed and range of the movement. In studying the action, then, of any particular muscle, there must be included the consideration of the antagonistic and the fixator muscles also. The movement of flexion is produced by flexor muscles, with the opposite extension produced by extensor muscles. Abdnctor muscles oppose adductors, and pronators oppose supinators. Inward rotators oppose outward rotators. The movement of circumduction is a combination of flexion, extension, abduction and adduction. It may vary in direction, inward or outward, but muscles are not named as producing this movement. METHODS OF STUDY. If the conformation of the bones has already been fixed in the mind's eye, by actual use of the bones during the study of the osseous system, it will render easier the study of muscles. After MOVEMENTS OF SEGMENTS OF THE UPPER EXTREMITY 135 learning the attachments of muscles, and finding the bony markings, paper or cloth patterns cut out in the size and shape of the muscles and applied to the skeleton, give a vivid idea of reality. The use of rubber bands or strings attached to the skeleton and made to imitate the muscular pull is also recommended. But the skeleton is not always available for study, but our own bodies are. Most of the superficial muscles can be felt contracting, and continuous examination of the areas contracting will help greatly in this study. MOVEMENTS OF THE SEGMENTS OF THE UPPER EXTREMITY. The shoulder-girdle moves upward, downward, forward and back upon the articulation of the clavicle with the sternum. The terms elevation, depression, abduction and adduction are used to indicate these movements. The arm moving at the shoulder-joint is raised forward in flexion, backward in extension, outward in abduction and inward in adduc- tion, inward and outward rotation and circumduction. The forearm moving at the elbow-joint is raised forward in flexion, and returns to the straight line in extension. (It should be noted that all the joints of the body when at rest are in a position midway between flexion and extension, or whatever other position is allowed.) At the upper radio-ulnar joint, the forearm turns inward in pro- nation, outward in supination. The hand moving at the wrist goes forward in flexion, backward in extension, outward in abduction and inward in adduction, while circumduction may be inward or outward. (Attention is called to the fact that in describing movements or positions the body is supposed to be standing erect, with arms hanging at the sides with the palms facing forward.) The fingers moving forward at the various phalangeal joints are in flexion, while the opposite move- ment is extension. This is true at the metacarpo-phalangeal joints, also, at which abduction and adduction occur from and toward the middle line of the second finger. The thumb bends toward the little finger in flexion, crossing the palm, and the reverse in extension. This is on account of the for- ward position of the first metacarpal bone, so the thumb is almost at a right angle with the fingers. Abduction of the thumb is toward the rear, while adduction is in the opposite direction. In these movements of the upper extremity, flexion is movement forward, but in the lower extremity, flexion and extension alternate in the forward direction, in the successive joints. The explanation lies in their different functions, prehension in the upper and loco- motion and balance in the lower segments. 136 THE MUSCULAR SYSTEM THE MUSCLES MOVING THE SHOULDER. Upu'ard and backward. Trapezius Levator scapulae Rhomboideus minor and major Downward and forward. Serratus rnagnus Pectoralis minor Subclavius Fig. 123.-Muscles in the superficial layer of the back. (Testut.) Trapezius.-In three parts. (Fig. 123.) Location.- Superficial on upper back and shoulder. Origin.- Superior curved line and protuberance of occiput; ligamentum nuchae; spines of seventh cervical and twelve thoracic vertebrae. THE MUSCLES MOVING THE SHOULDER 137 Insertion.- Outer third of posterior border of clavicle. Inner border of acromion and upper border of spine of scapula. Tubercle of spine near its inner end. Fig. 124.-Muscles in the second layer of the back and on the dorsum of the shoulder, (Testut.) Nerve Supply. -Spinal accessory and third and fourth cervical. Action.- With head fixed, upper fibers lift outer end of clavicle with scapula. With scapula fixed, one side rotates the head; both sides pull the head backward. Middle fibers, lifts acromion; adducts scapula. Lower fibers, pulls vertebral border of scapula down and in. As a whole, rotates scapula to turn the glenoid fossa upward and outward. 138 THE MUSCULAR SYSTEM Levator Scapulae. - (O. T. levator anguli scapulae). (Fig. 124.) Location.- On the side of the neck, under the trapezius. Origin.-Upper four or five cervical vertebrae, on transverse processes. Fig. 125.-Serratus magnus of right side. The scapula has been turned back- ward and drawn outward. (Modified from Testut.) Insertion.- Vertebral border of scapula from superior angle to root of spine. Nerve Supply.- Third, fourth and fifth cervical. Action.- Lifting upper angle of scapula with depression of the outer end. Rhomboideus Minor. (Fig. 124.) Location.-Between the scapula and spine, underneath the trapezius. THE MUSCLES MOVING THE SHOULDER 139 Origin.-Ligamentum nuchee; spines of seventh cervical and first thoracic vertebrae. Insertion.-Vertebral border of scapula at root of spine. Nene Supply.- Fifth cervical. Action.- Adducts and elevates the scapula with some rotation. Fig. 126.-Pectoralis minor of right side. (Testut.) Rhomboideus Major. (Fig. 124.) Location.-Just below the minor. Origin.- Spines of the upper four or five thoracic vertebrae. 1 nsertion.- Vertebral border of scapula, below that of the minor. Nene Supply.- Fifth cervical. Action.- Adducts and elevates the scapula. Serratus Magnus. -(Fig. 125.) Location. -Anterior to the scapula on the upper side of the chest. Origin.-By digitations, in three parts. Upper part, from first and second ribs, several inches from their ends. Middle part, from second and third ribs. Lower part, from fourth to eighth ribs. 4 140 THE MUSCULAR SYSTEM Insertion.-Upper part to ventral border of the superior angle. Middle part to ventral surface of vertebral border, except angles. Lower part to ventral border of the lower angle. Nene &upph/.-Posterior thoracic. Action.- The upper and middle parts draw the shoulder for- ward as in pushing, while the lower part rotates the scapula, turning the glenoid fossa upward as in raising the arm. Pectoralis Minor. (Fig. 126.) Location.-On the front wall of the chest, covered by the large pectoral. Origin.- Third, fourth and fifth ribs, near their cartilages. Insertion.-Coracoid process of the scapula. Nene Supply.- Internal anterior thoracic. Action.-When chest is fixed, draws scapula down and for- ward. When scapula is fixed, draws the chest upward, as in forced inspiration. Subclavius. (Fig. 126.) Location.-Under the clavicle. Origin.- The first rib and its cartilage. Insertirm.-N groove on the under surface of the clavicle. Nene Supply.-Filth and sixth cervical. Action.- Depresses the scapula and turns the glenoid fossa downward. THE MUSCLES MOVING THE ARM. Abductors. Deltoideus Supraspinatus Adductors. Pectoralis major Coracobrachialis also flexors Latissimus Teres major aIs0 extensors Outward rotators. Infraspinatus Teres minor Inward rotator. Subscapularis Deltoideus. (Fig. 127.) Location.- Forming a cap over the shoulder-joint. Origin. -Anterior border of the outer third of the clavicle. Acromion process, and lower border of the spine of the scapula. Insertion.-The deltoid impression, midway of the outer sur- face of the humerus. Nene Supply.- The circumflex. Action. -Abduction of the arm. The anterior fibers carry the arm forward, the posterior fibers carry it backward. Supraspinatus. (Fig. 128.) Location.-In the supraspinous fossa, covered by the trapezius. THE MUSCLES MOVING THE ARM 141 Origin.-Inner two-thirds of supraspinous fossa. Insertion.- The uppermost facet on the greater tuberosity of the humerus. Nerve Supply.- The suprascapular. Action.- Abducts the arm. Fig. 127.-Front of chest and shoulder of right side, superficial muscles. (Testut.) Pectoralis Major. (Fig. 127.) Location.-Covers the front wall of the chest. Origin.- The inner half of the anterior border of the clavicle. The anterior surface of the sternum. The cartilages of the upper six ribs. Insertion.-The outer lip of the bicipital groove of the humerus. Nerve Supply.-Internal and external anterior thoracic. Action.-Sternal portion helps to flex the arm. All portions draw the arm across the chest. 142 THE MUSCULAR SYSTEM Coracobrachialis. (Figs. 129, 130.) Location.- On the inner side of the upper part of the arm. Origin.-The coracoid process of the scapula. Insertion. -The middle of the inner border of the humerus. Nene Supply.-The muscuolcutaneous. Action.-Flexion and adduction of the arm. Fig. 128.-Muscles on the dorsum of the right shoulder and arm. (Testut.) Latissimus.-(O. T. latissimus dorsi). (Fig. 123.) Location.-The lower part of the back and the axilla. Origin.-Spines of six lower thoracic, all the lumbar and sacral spines. The lumbar fascia; the outer lip of the iliac crest, hind part. The three or four lower ribs, and the lower angle of the scapula, THE MUSCLES MOVING THE ARM 143 Insertion.- The inner lip and floor of the bicipital groove of the humerus. Nene Supply.- Long subscapular. Action.-Extension, adduction and inward rotation of the arm. Fig. 129.-Muscles of the front of the right shoulder and arm. (Testut.) Teres Major. (Fig. 124.) Location.-In the posterior wall of the axilla. Origin. - The dorsal surface of the axillary border of the scapula, lower half. Insertion.- The inner lip of the bicipital groove of the humerus. 144 THE MUSCULAR SYSTEM Nerve Supply.-Lower subscapular. Action.-Helps the latissimus in extension, adduction and inward rotation of the arm. Fig. 130.-Muscles of the right arm, front view, the biceps having been removed. (Testut.) Infraspinatus. (Fig. 124.) Location.-On the back of the scapula, partly covered by the trapezius. Origin.-Infraspinous fossa, inner two-thirds. Insertion.-Middle facet on the greater tuberosity of the humerus. THE MUSCLES MOVING THE FOREARM 145 Nerve Supply.- Suprascapular. Action.- Rotates the arm outward. Teres Minor. (Fig. 124.) Location.-In the posterior wall of the axilla. Origin.-Dorsal surface of axillary border of the scapula, upper half. Insertion.-The lowermost facet on the greater tuberosity of the humerus. Nerve Supply.-Circumflex. Action.-Rotates the arm outward. Subscapularis. (Fig. 125.) Location.-The under surface of the scapula, next the chest wall. Origin.-The ventral surface of the scapula, in the subscapular fossa. Insertion.- The lesser tuberosity of the humerus. Nerve Supply.-Upper and lower subscapular. Ac/ion.-Rotation inward of the humerus. THE MUSCLES MOVING THE FOREARM. Flexors. Biceps flexor cubiti Brachialis Brachio-radialis Extensors. Triceps extensor cubiti Anconeus Biceps Flexor Cubiti. (Fig. 129.) Location.-On the front of the arm, superficial. Origin.- Long head, the upper border of the glenoid fossa. Short head, the coracoid process of the scapula. Insertion.-The bicipital tuberosity of the radius. Nerve Supply.-The musculocutaneous. JcZion.-Flexes the forearm. The long head acts to Hex the arm at the shoulder-joint. If the hand is pronated, the biceps supinates it. If the forearm is in supination, the biceps flexes it more easily. Brachialis. -((). T. brachialis anticus or anterior). (Fig. 130.) Location.- The lower front of the arm, deeply placed. Origin.-The lower half of the ventral surface of the arm, embracing the insertion of the deltoideus. Insertion.-The coronoid process of the ulna. Nerve Supply.- Musculocutaneous, and to some degree, the musculospiral. Action.-Flexes the forearm. Brachio-radialis. -(O. T. supinator longus). (Figs. 131, 132.) Location.-The outer side of the forearm, superficial. 146 THE MUSCULAR SYSTEM Origin. -Upper two-thirds of the external supracondylar ridge of the humerus. Insertion.-The styloid process of the radius. Fig. 131.-Superficial muscles of front of right forearm. (Testut.) Fig. 132.-Flexor sublimis digitorum of right side. (Testut.) Nerve Supply.- Musculospiral. Action.-Flexion of the forearm, especially in the position midway between pronation and supination. Fig. 133. Muscles in the dorsum of the right forearm and hand. (Testut.) 148 THE MUSCULAR SYSTEM Triceps Extensor Cubiti. (Fig. 128.) Location.-On the back of the arm. Origin.-Long head, the lower border of the glenoid fossa. Inner head, the posterior surface of the humerus, below the musculospiral groove. Outer head, the posterior surface of the humerus, above same. Insertion.-The back of the upper part of the olecranon process of the ulna. Nerve Supply.- Musculospiral. Action.-Extends the forearm. The long head extends the arm, acting with the latissimus. Anconeus. (Figs. 128, 133.) Location.- Back and outer side of the elbow-joint. Origin.- The external condyle of the humerus. Insertion.- Outer side of olecranon process and upper dorsal surface of ulna. Nerve Supply.- Musculospiral. Action.-A helper of the triceps in extending the forearm. THE MUSCLES MOVING THE OUTER PART OF THE FOREARM. Pronators. Pronator teres Pronator quadratus Supinator. Supinator Pronator Teres.-(O. T. pronator radii teres). (Fig. 131.) Location.-Crosses over the front of the forearm, from within, outward. Origin.-The inner condyle of the humerus. Insertion.-The middle of the outer surface of the shaft of the radius. Nerve Supply.-The median. .1 (4cm.-Pronation of the hand, and if that is prevented, flexion of the forearm. Pronator Quadratus. (Fig. 134.) Location.-Deep in the lower part of the front of the forearm. Origin.-The lower fourth of the anterior surface of the ulna. ] nsertion.-The lower fourth of the anterior surface of the fadius. Nerve Supply.-Anterior interosseous branch of the median. Action.-Pronates the hand, turning the radius over the ulna. Supinator. -(O. T. supinator brevis). (Fig. 135.) Location.-Deep in the upper third of the outer part of the forearm. Origin.--The external condyle of the humerus; the triangular area below the lesser sigmoid cavity of the ulna. Fig. 134.-Muscles in the right forearm, the deepest layer. (Testut.) Fig. 135.-Supinator of right side. (Testut.) 150 THE MUSCULAR SYSTEM Insertion.-The back of the neck of the radius, and the poste- rior, outer surface of the same above the oblique line. Nerve Supply.-Posterior interosseous division of the musculo- spiral. Action.- Supinates the forearm, assisting the brachio-radialis, and serving as a supplementary ligament to the elbow- joint. THE MUSCLES MOVING THE WHOLE HAND. Flexors. Flexor carpi radialis (Flexor) palmaris longus Flexor carpi ulnaris Extensors. Extensor carpi radialis longus Extensor carpi radialis brevis Extensor carpi ulnaris The extensor muscles of the forearm and the supinator may be remembered as coming from the external condyle of the humerus or just above it. The flexor and pronator muscles come from the internal condyle, and are associated in action. Note the greater ease in piano playing, of running from the little finger to the thumb, than the reverse. The movements at the wrist, besides flexion and extension are adduction and abduction, which are performed by the combined action of a flexor and extensor, on the ulnar and radial sides respec- tively. Flexor Carpi Radialis. (Fig. 131.) Location.- Superficial on the front of the forearm, crossing diagonally. Origin.-Inner condyle of the humerus. Insertion.- The base of the second metacarpal bone, on its palmar aspect. Nerve Supply.- The median. fiction.-Flexion on radial side and pronation of hand. Helps the radial extensor to abduct the hand. Palmaris Longus. (Fig. 131.)-A very small muscle, with a long tendon, coming from the internal condyle to the palmar fascia, which it makes tense. Does a little toward flexion. This muscle is quite frequently lacking. Flexor Carpi Ulnaris. (Figs. 131, 133.) Location.- On the front and inner aspect of the forearm. Origin.-Inner condyle of the humerus. Inner side of the olecranon process and the common aponeurosis on the dorsal border of the ulna, from which proceeds the extensor carpi ulnaris and the flexor pro- fundus digitorum. Fig. 136.-Muscles in radial region of right forearm, and deep muscles in its dorsum. (Testut.) 152 THE MUSCULAR SYSTEM Insertion.- The pisiform, unciform and the base of the fifth metacarpal on the palmar aspect. Nene Supply.- Ulnar. A ction.-Flexes the hand on the ulnar side. Helps the ulnar extensor to adduct the hand. Extensor Carpi Radialis Longus. (Fig. 136.) Location.-On the outer border of the forearm. Origin.-The lower part of the external supracondylar ridge of the humerus. Insertion.-The base of the metacarpal of the first finger, pos- teriorly. Nene Supply.- Musculospiral. Action.- Extends the hand on radial side. Extensor Carpi Radialis Brevis. (Fig. 136.) Location. - The outer part of the forearm, posteriorly. Origin.-The external condyle of the humerus. Insertion.- The base of the metacarpal of the second finger, posteriorly. Nene Supply.-Posterior interosseous branch of the musculo- spiral. Action.- Extends the hand. Extensor Carpi Ulnaris. (Fig. 133.) Location.-On the ulnar side of the back of the forearm. Origin.- External condyle of the humerus and posterior border of the ulna. Insertion.-Base of the fifth metacarpal bone, on its posterior aspect. Nene Supply.-Posterior interosseous branch of the musculo- spiral. A ction.-Extends the hand on the ulnar side, and with the ulnar flexor, adducts the hand. Note that the "carpi" muscles are inserted into the metacarpal bones but move the wrist-joint. Note that all the extensor muscles are supplied by the musculo- spiral nerve. THE MUSCLES MOVING THE FINGERS. posteriorly. Flexors. Flexor sublimis digitorum Flexor profundus digitorum *Flexor ossis metacarpi minimi digiti *Flexor brevis minimi digiti *Lumbricales Extensors. Extensor communis digitorum Extensor minimi digiti Extensor indicis * These muscles are situated entirely in the hand. THE MUSCLES MOVING THE FINGERS 153 Flexor Sublimis Digitorum. (Fig. 132.) Location.-On the front of the forearm and the palm of the hand. Origin.- The internal condyle of the humerus. The coronoid process of the ulna, and the oblique line of the radius. Insertion.- The sides of the base of the second phalanx of the four fingers. Above the wrist, the tendon divides into four parts, which pass under the annular ligament, through the palm of the hand, and on to the base of the second phalanx of each finger, where the tendons divide, going to each side of the bone, and leav- ing a slit through which the tendon of the deep flexor has to pass to get to the base of the third phalanx. Nene Supply.- The median. Action.-Flexes the second phalanx of each of the fingers. Con- tinuing to contract, it flexes secondarily, the first phalanx. Flexor Profundus Digitorum. (Figs. 134 and 137.) Location.-Deep in the front of the forearm, next the bone, and in the hand. Origin.- The upper three-fourths of the ventral surface of the ulna. The adjacent interosseous mem- brane. The posterior border of the ulna, in common with the extensor carpi ulnaris and the flexor carpi ulnaris. Insertion.- The base of the third phalanx of the four fingers. Above the wrist the tendon divides into four slips, which pass into the hand, under those of the superficial flexor, and go up through the slit in the latter tendon to the distal phalanx. Nene Supply.-Ulnar and anterior interosseous branch of the median. A ction.-Flexes the third phalanx of the four fingers. Flexor Ossis Metacarpi Minimi Digiti. (Fig. 138) (O. T. Opponens minimi digiti.)-A small muscle deep in the hypothenar emi- nence, whose action draws the sides of the hand together, Fig. 137.-Tendon of flexor profundus perforating tendon of flexor sublimis. (Testut.) 154 THE MUSCVLAR SYSTEM Fig. 138.-Muscles of the right palm. The abductors of the thumb and little finger have been removed. (Testut.) THE MUSCLES MOVING THE FINGERS 155 Fig. 139. Muscles of the right palm. The palmaris brevis is reflected to the ulnar side. (Testut.) 156 THE MUSCULAR SYSTEM deepening the palm. It originates in the wrist and passes to the palmar side of the little finger metacarpal. Flexor Brevis Minimi Digiti. (Fig. 138.) Location.-In the palm of the hand, on the ulnar side, subcu- taneously. Origin.-Unciform process of the unciform bone and the annu- lar ligament. Insertion.-Base of the first phalanx of the little finger. Nerve Supply.-Ulnar. Action.- Flexes the first phalanx of the little finger. Lumbricales. (Figs. 138, 139.)-Four small muscles pass from the tendons of the flexor profundus digitorum to those of the exten- sor communis digitorum. They are small, and so-called from their resemblance to earth worms. They flex the first phalanx of the fingers, and extend the second and third. Extensor Communis Digitorum. (Fig. 133.) Location.-On the back of the forearm and hand, superficial. Origin.-The external condyle of the humerus. Insertion.-The base of the second and third phalanges of each finger. Above the wrist, the tendon divides into four slips, which pass under the annular ligament, and then to the fingers. Each slip divides into three parts, the middle one attaching to the base of the second phalanx and the other two uniting to be attached to the base of the third phalanx of the fingers. The name "communis" refers to the fact that the tendinous attachment is to the two phalanges by a common tendon. Nerve Supply .-Posterior interosseous branch of the musculo- spiral. Action.-Extends the second and third phalanges of the fingers. Extensor Minimi Digiti. (Fig. 133.) Location.-In the back of the forearm and hand. Origin.-External condyle of the humerus. Insertion.- Second and third phalanges of the little finger. Nerve 8 wppZy.-Posterior interosseous branch of the musculo- spiral. Action.-Extends the second and third phalanges of the little finger. Extensor Indicis. (Fig. 136.) Location.-In back of forearm and hand. Origin.- Lower part of the dorsal surface of the ulna and in(ei osseous membrane. Insertion.-The first tendon of the extensor communis digi- torum. Nerve SuppZy.-Posterior interosseous branch of the musculo- spiral. THE MUSCLES MOVING THE FINGERS 157 Action.-Independent extension of the first finger, and slight adduction. Abductors and Adductors of the Fingers. (Figs. 139, 140, 141.) - The fingers are abducted from the line passing through the second finger by four small muscles, the interossei dorsales. These originate from the contiguous sides of the five metacarpal bones, and the tendons are inserted on the first phalanges so that the first and second pull the first and second fingers from the central line. The Fig. 140.-Interossei dorsales of right hand. The line a; a: is that from which abduction is made. (Testut.) third and fourth pull the second and third fingers from the central line. When the second tendon pulls the second finger toward the thumb side, it is adducted by the tendon attached on the ulnar side of this finger, and a similar condition results when the third tendon pulls the second finger toward the ulnar side. The second and third interossei dorsales muscles therefore act as abductors and adductors. The interossei palmares, coming from the second, fourth and fifth metacarpal bones, are inserted into the bases of the corresponding 158 THE MUSCULAR SYSTEM fingers, and adduct them toward the line passing through the middle of the second finger. The little finger has a special abductor, on the palmar surface, coming from the pisiform bone to the base of the first phalanx of the little finger. These muscles are all supplied by the ulnar nerve. Fig. 141.-Interossei palmares of right hand. The line a; a: is that to which adduction is made. (Testut.) THE MUSCLES MOVING THE THUMB AND ITS METARCARPAL BONE. Flexors. *Elexor ossis metacarpi pollicis *Flexor brevis pollicis Flexor longus pollicis Extensors. Extensor ossis metacarpi pollicis Extensor brevis pollicis Extensor longus pollicis Abductor. *Abductor pollicis * Entirely in the hand. Adductor. * Adductor pollicis THE MUSCLES MOVING THE THUMB 159 Fig. 142.-Adductor pollicis, flexor ossis metacarpi pollicis and pronator quadratus. (Testut.) 160 THE MUSCULAR SYSTEM Flexor Ossis Metacarpi Pollicis.-(O. T. Opponens pollicis.) (Figs. 138, 142.) Location.-Deep in the thenar eminence. (Thenar eminence, the ball of the thumb.) Origin.-Trapezium and annular ligament, on the palmar aspect. Insert ion.- Shaft of the first metacarpal bone, on the front of the radial side. Nerve Supply.-Median. Action.-Flexes and rotates the first metacarpal inward. Flexor Brevis Pollicis. (Fig. 138.) Location.-Deep in the ball of the thumb. Origin.-Trapezium and annular ligament on the radial side, palmar aspect. Upper part of the first metacarpal on the ulnar side. Insertion.- First part, outer side of the base of the first phalanx of the thumb, with the abductor pollicis. Second part, inner side of the base of the first phalanx of the thumb, with the adductor pollicis. With each of these tendons there is a small sesamoid bone. Nerve Supply.-The first part, the median; second part, the ulnar. Action.- Flexes the first phalanx of the thumb. Flexor Longus Pollicis. (Fig. 134.) Lccation.-Front part of forearm and palmar aspect of the thumb. Origin.-Oblique line of radius, and middle two-thirds of shaft. Interosseous membrane adjoining. Insertion.-Base of second phalanx of the thumb, palmar aspect. Nerve Supply.-Anterior interosseous branch of the median. Action.-Flexes the second phalanx of the thumb. Extensor Ossis Metacarpi Pollicis. -(O. T. Abductor longus pollicis.) (Fig. 136.) Location.-Deep in the lower part of the back of the forearm. Origin.-The posterior shaft of the radius and ulna, with mem- brane between. Insertion.-Base of the first metacarpal bone, dorsally. Nerve Swppb/.-Posterior interosseous branch of the musculo- spiral. Action.-Extension and abduction of the first metacarpal bone. Extensor Brevis Pollicis. -(O. T. Extensor primi internodii pollicis.) (Fig. 136.) Location. - Deep in the lower part of the back of the forearm. Orh/in.-Middle of the posterior shaft of the radius, and adja- cent membrane. Insertion.-Base of the first phalanx of the thumb, on dorsal aspect. ulnar. THE MUSCLES OF THE LOWER EXTREMITY 161 Nerve Supply.-Posterior interosseous branch of the musculo- spiral. Action.-Extends the first phalanx of the thumb. Extensor Longus Pollicis. -(0. T. Extensor secundi internodii pol- licis.) (Fig. 136.) Location.-Deep in the lower part of the back of the forearm. Origin.- Middle of the posterior shaft of the ulna and adjacent membrane. Insertion. - The base of the second phalanx of the thumb, dorsal aspect. Nerve Supply.-Posterior interosseous branch of the musculo- spiral. Action.-Extends the second phalanx of the thumb. Abductor Pollicis. (Fig. 139.) Location.- Superficial on the ball of the thumb. Origin.- Trapezium, scaphoid and annular ligament, palmar aspect. Insertion.-Base of the first phalanx of the thumb, on the radial side. Nerve Supply.-Median. Action.-Abducts the thumb. Adductor Pollicis. (Fig. 142.) . Location.-Deep in the radial side of the palm. Origin.-Os magnum, bases of second and third metacarpal bones, and annular ligament. Lower two-thirds of the third metacarpal shaft, palmar aspect. Insertion.-Inner side of the base of the first phalanx of the thumb. Nerve Supply.-Ulnar. Action.- Adduction and flexion of first phalanx of thumb. THE MUSCLES OF THE LOWER EXTREMITY. Movements of the Thigh.-As the hip-joint is a ball-and-socket joint, all kinds of movement are possible here, as in the shoulder- joint, though there is less freedom. Forward movement of the thigh is flexion; backward movement is extension; sideways outward is abduction; sideways inward is adduction; circumduction is the com- bination of these and rotation takes place as in the arm. . Movements of the Leg.-At the knee-joint, flexion is movement backward; extension is forward; and the small amount of rotation at the end of extension and beginning of flexion is respectively outward and inward. Movements of the Foot.-At the hinge of the ankle, movement upward is flexion; movement downward is extension. The move- ment of inversion, turning the sole toward the middle line, and its 162 THE MUSCULAR SYSTEM reverse of eversion takes place at the medio-tarsal and astragalo- calcaneal joints. Movements of the Toes.-Flexion of the toes is movement down- ward; extension is movement upward, while adduction and abduction take place at the metatarso-phalangeal joints, toward and from the middle line of the second toe. THE MUSCLES MOVING THE THIGH. Flexors. Psoas magnus Iliacus Extensor. Gluteus maximus Abductors. Tensor fasciae latae Gluteus medius Gluteus minimus Adductors. Adductor magnus Adductor longus Adductor brevis Adductor gracilis Pectineus Internal rotators. Tensor fasciae latae Gluteus medius Gluteus minimus Outward rotators. Obturator externus Obturator internus Pyriformis Gemellus superior Gemellus inferior Quadratus femoris Psoas Magnus or Major. -(Fig. 143.) Location.-Back part of the abdomen and upper part of thigh. Bodies of the last thoracic and all the lumbar vertebrae and the cartilages between, with the transverse processes. Insertion.-The lesser trochanter of the femur. Nene Supply.-Second and third lumbar. Action.-Flexion of the thigh and outward rotation. Iliacus. (Fig. 143.) Location.-In the hind wall of the abdomen and upper part of the thigh. Origin.-The iliac fossa, and the ala of the sacrum. Insertion.-The lesser trochanter, along with the psoas magnus. Nene Supply. - Anterior crural. Action.- With the psoas, it flexes and rotates the thigh out- wardly. These two muscles are often referred to as one, the psoas magnus. Gluteus Maximus. (Fig. 144.) Location.-Forming most of the buttock. 163 THE MUSCLES MOVING THE THIGH Outer lip of the iliac crest (posterior fourth). Dorsal surface of the ilium between the crest and superior gluteal line; two lower segments of the sacrum and the coccyx. The aponeurosis of the erector spina?. Fig. 143.-Psoas, iliacus and obturator externus muscles. (Testut.) Insertion.-Gluteal ridge of femur and fascia lata. Nene Supply.-Inferior gluteal. Action.-Extension of the thigh and outward rotation. Tensor Fasciae Latae.-(O. T. Tensor vaginae femoris.) (Fig. 145.) Location.-Upper and outer aspect of the thigh, anteriorly. 164 THE MUSCULAR SYSTEM Origin.-Just below the crest of the ilium, back of the anterior- superior spine. Insertion.-Into the fascia lata, below the great trochanter. Nerve Supply. - Superior gluteal. Action.- Abduction and inward rotation of the thigh; tensing the fascia lata. Gluteus Medius. (Fig. 146.) Location.- Outer part of the hip, forming part of the buttock. Origin.- The space between the superior and middle gluteal ridges of the ilium. Fig. 144.-Gluteus maximus of right side. (Testut.) Insertion.-Outer surface of the great trochanter. Nerve Supply.-Superior gluteal. Action.-Abduction of the thigh when it is extended, and inward rotation of the thigh when it is flexed. Gluteus Minimus. (Fig. 147.) Location.-The outer part of the hip, under the medius. Origin.-Between the middle and inferior gluteal ridges, on the dorsum of the ilium. Insertion.-The front of the great trochanter. 165 THE MUSCLES MOVING THE THIGH Nerve Supply. -Superior gluteal. Action.-Abduction of the extended, inward rotation of the flexed thigh. Fig. 145.-Superficial muscles in front part of the right thigh. (Testut.) Adductor Magnus. (Figs. 148, 149.) Location.-The full length of the inner side of the thigh. Fig. 146.-Muscles of right hip, viewed from behind the gluteus maximus having been cut away. (Testut.) Fig. 147.-Gluteus minimus of right side. (Testut.) THE MUSCLES MOVING THE THIGH 167 Origin.-Rami of pubis and ischium, and the ischial tuberosity. Insertion.-Gluteal ridge, inner lip of linea aspera, internal condylar ridge and adductor tubercle of femur. Fig. 148.-Adductores magnus and brevis of right side. (Testut.) Fig. 149.-Muscles in deep por- tion of dorsum of right thigh, the semitendinosus and most of the biceps having been removed. (Testut.) 168 THE MUSCULAR SYSTEM Nerve 8t/ppZ?/.-Obturator and great sciatic. Acticm.-Adduction of thigh and outward rotation. The fibers coming from the ischial tuberosity extends the thigh upon the hip. Fig. 150.-Muscles in the right thigh, viewed from in front, after removal of the rectus and sartorius. (Testut.) Fig. 151.-Muscles in the dorsum of the right thigh. (Testut.) 169 THE MUSCLES MOVING THE THIGH Adductor Longus. (Fig. 150.) Location.-Inner side of the thigh. Origin.-Body of the pubic bone near the angle. Insertion.-The middle third of the linea aspera, inner lip. Nerve Supply.- Obturator. Action.- Adducts, flexes and outwardly rotates the thigh. Adductor Brevis. (Fig. 148.) Location.-Inner and upper side of the thigh. Origin. - Body and descending ramus of the os pubis. Insertion.-Upper part of the linea aspera. Nerve Supply.-Obturator. Action.- Adducts, flexes and outwardly rotates the thigh. Adductor Gracilis. (Fig. 150.) Location.-Inner side of the thigh and back of knee. Origin.-Descending ramus and symphysis of the os pubis. Insertion.-Upper part of the inner aspect of the tibia, near the tubercle. Nerve Supply.-Obturator. Action.-Flexes the leg, and inwardly rotates it. Pectineus. (Fig. 150.) Location.-Between the front of the pelvis and the back of the thigh. Origin.-Iliopectineal line of ilium, and surface in front of it. Insertion. -Upper half of the pectineal line behind the small trochanter. Nerve Supply.-Anterior crural, and sometimes the obturator. Action.- Adducts, flexes and slightly rotates the thigh out- wardly. Obturator Extemus. (Fig. 148.) Location.-Outer surface of the pelvis. Origin.-The outer surface of the obturator membrane, the con- tiguous bony surface and the rami of the os pubis and ischium. Insertion.-Bottom of the digital fossa. Nerve Supply.-Obturator. Action.- Adducts and rotates thigh outwardly. Obturator Interims. (Fig. 151.) Location.-On the inner wall of the pelvis. Origin.-Inner surface of the obturator membrane; margin of foramen; and space between the foramen, iliopectineal line and great sacro-sciatic foramen. Insertion.- Inner surface of great trochanter, toward the front. Nerve Supply.-Branch from the sacral plexus. Action.-Outward rotation, when thigh extended; abducts the thigh when flexed. 170 THE MUSCULAR SYSTEM Pyriformis. (Fig. 146.) Location.-On the posterior wall of the true pelvis. Origin -Posterior border of ilium below the inferior spine; ventral surface of the second, third and fourth segments of the sacrum. . Insertion.-Upper border of great trochanter, anteriorly. Nerve Supply.-Branch from the sacral plexus. Action.-Outward rotation when thigh is extended; abducts when flexed. Gemellus Superior and Inferior. (Fig. 146.)-Two small muscles, one above, the other below the obturator internus, and assisting in its work with similar insertion. Quadratus Femoris. (Fig. 146.) Location.- Back of the hip-joint. Origin.-Outer border of the ischial tuberosity. Insertion.- Quadrate line on back of femur. Nerve Supply.-Branch from the sacral plexus. Action.-Adducts and outwardly rotates thigh. THE MUSCLES MOVING THE LEG. Flexors. *Sartorius *Biceps flexor cruris *Semitendinosus *Semimembranosus Popliteus Extensors. Quadriceps extensor cruris, com- prising **Rectus femoris Vastus lateralis Vastus medialis Vastus intermedins * These four flexors of the leg, cross the hip-joint as well, and act to extend the thigh, if flexion of the leg is prevented or is com- pleted. ** This muscle passing over both the hip- and knee-joints, acts as a flexor of the thigh, when the leg is fully extended or the knee held in a flexed position so it cannot extend. Sartorius. (Fig. 145.) Location.-On the front of the thigh crossing over to the inner side of the knee. Anterior-superior spinous process of the ilium, and just below. Insertion.- The upper part of the inner aspect of the tibia, near the tubercle. Nerve Supply.-Anterior crural. Action.-Flexes the leg and thigh with synchronous abduction of the thigh; then outward rotation. Biceps Flexor Cruris. (Fig. 151.) Location.-In the back of the thigh and knee-joint. 171 THE MUSCLES MOVING THE LEG Origin.-Long head, the tuberosity of the ischium. Short head, the lower part of the linea aspera and upper two-thirds of the external condylar ridge. Insertion.-The head of the fibula. Nene Supply.-Great sciatic. Action.-Flexes the leg, with external rotation. Extends the thigh. Semitendinosus. (Fig. 151.) Location.-Inner side of the back of the thigh. Origin.-Tuberosity of the ischium. Insertion.-Upper part of the inner aspect of the tibia, near the tubercle. Nene Supply.-Great sciatic. Action.-Viexes the leg, then rotates it inward. Extends the thigh. Semimembranosus. (Figs. 149, 151.) Location.-Inner side of the back of the thigh. Origin.-Tuberosity of the ischium. Insertion.-A groove on the inner and posterior aspect of the inner tuberosity of the tibia. Nene Supply.-Great sciatic. Action.-Flexes leg, than rotates it inward. Extension of the thigh. Note.-The tendons of the gracilis, semitendinosus and semi- membranosus, form the "inner hamstrings." The tendon of the biceps flexor cruris forms the "outer hamstring." Popliteus. (Fig. 149) Location.-Back of the knee, close to the joint. Origin.-The outer side of the external condyle of the femur. Insertion.-Above the oblique line of the tibia, on a triangular area. Nene Supply .-Internal popliteal branch of the great sciatic. Action.-Flexes and rotates leg inward. The Quadriceps Femoris (Quadriceps extensor cruris) is a com- pound of four muscles, placed on the thigh and enveloping it, front and sides, leaving only part of the linea aspera uncovered. The insertion of the combination is through one large tendon, to the tubercle of the tibia. In this tendon is developed the sesamoid bone, the patella. Rectus Femoris. (Fig. 145.) Origin.-Anterior-inferior spine of the ilium and a reflected tendon from above the acetabulum. Insertion.-The tubercle of the tibia. Nene Supply.-Anterior crural. Action.-Extends the leg and flexes the thigh. thigh. thigh. 172 THE MUSCULAR SYSTEM Vastus Lateralis. - (O. T. Vastus externus.) (Figs. 150 and 152.) Location.-On the outer and back part of the thigh. Origin.-Anterior intertrochanteric line; base of great trochan- ter; the gluteal ridge and the outer lip of the linea aspera. Insertion.-The tubercle of the tibia. Nene Supply.-Anterior crural. Action.-Extends the leg. Fig. 152.-Vastus intermedins of right side. (Testut.) Vastus Medialis. -(O. T. Vastus internus.) (Figs. 150, 152.) Location.-On the inner part of the thigh. Origin.-Spiral line, inner lip of linea aspera, and internal supracondylar ridge. Insertion.-The tubercle of the tibia. Nene Supply.-Anterior crural. Action.-Extends the leg. THE MUSCLES MOVING THE FOOT 173 Vastus Intermedius. - (O. T. Crureus.) (Fig. 152.) Location.-Deep on the front of the thigh. Origin.-The upper two-thirds of the shaft of the femur, ante- riorly. Insertion.-The tubercle of the tibia. Nerve Supply.-Anterior crural. Action.-Extends the leg. A few muscular fibers arise from the lower part of the femur, and are inserted into the synovial membrane of the knee-joint. This is the musculus articularis genu, or muscle of the knee-joint. Its function is to pull the synovial membrane out of the way of being pinched in extension of the knee. THE MUSCLES MOVING THE FOOT. Flexors. Tibialis anterior Peroneus tertius Extensors. Tibialis posterior on inner side Gastrocnemius Soleus Plantaris in the center Peroneus longus Peroneus brevis on outer side Tibialis Anterior. -((). T. Tibialis anticus.) (Fig. 153.) Location.-On the front and outer side of the tibia. Origin.-Outer tuberosity and upper two-thirds of the external surface of the tibia and adjacent interosseous membrane. Insertion.-Inner surface of the internal cuneiform bone, and the base of the first metatarsal. Nerve Supply.-Anterior tibial branch of the great sciatic. Action.-Flexes the foot upon the leg, raises the inner border and adducts the front of the foot. Or flexes and inverts foot. Peroneus Tertius. (Fig. 153.) Location.-Lower front part of the leg. Origin.-Lower fourth of the anterior surface of the fibula and adjacent membrane. Insertion.-Base of the fifth metatarsal, upper surface. Nerve Supply.-Anterior tibial branch of the great sciatic. Action.-Flexes foot, raises outer border and abducts front or inversion. Tibialis Posterior. -(O. T. Tibialis posticus.) (Figs. 154, 155.) Location.-Deep in the back of the leg, and crossing the sole of the foot. On'grm.-The lateral half of the middle third of the posterior surface of the tibia. LTpper two-thirds of the shaft of the fibula and the interosseous membrane adjacent. Fig. 153.-Muscles in the right leg, viewed from in front. (Testut.) Fig. 154.-Tibialis posterior of right side. (Testut.) Fig. 155.-Muscles in the deep layer of the dorsum of the right leg. (Testut.) Fig. 156.-Gastrocnemius of right side. (Testut.) 176 THE MUSCULAR SYSTEM Fig. 157.-Muscles in the outer side of right leg and dorsum of foot. (Testut.) THE MUSCLES MOVING THE FOOT 177 Insertion.-Tuberosity of the scaphoid, with off-shoots to the three cuneiform, the cuboid, the bases of the second, third and fourth metatarsals, and to the sustentaculum tali of the calcaneum. (Thereby getting a grip on the entire sole, after passing back of the inner malleolus. Very important in maintaining the arch of the foot.) Nerve Supply.-Posterior tibial branch of the great sciatic. Action.-Extends the foot on the leg; raises the inner border and adducts the front of the foot. Or extends and inverts foot. Gastrocnemius. (Figs. 156, 157.) Location.-Superficial in the calf of the leg. Origin.-By two heads, from the inner and outer condyles of the femur, and just above. Insertion.-The back of the calcaneum, by the tendo Achillis. Nerve Supply .-Internal popliteal branch of the great sciatic. Action.-Extends the foot upon the leg. Flexes the leg on the thigh. Soleus. (Figs. 157, 158.) Location.-Deep in the calf of the leg. Origin.-Head and upper third of the posterior surface of the fibula. Oblique line and inner border of tibia to the middle of the shaft. Insertion.-The back of the calcaneum, by the tendo Achillis. Nerve Supply .-Internal popliteal and posterior tibial branches of the great sciatic. Action.-Extends foot on leg. By extension of foot, the weight of the body is raised. Plantaris.-A small muscle, arising from above the external condyle of the femur, and inserted with the above two. Slight action in extending foot and flexing leg. (Fig. 158.) Peroneus Longus. (Figs. 155, 157 and 159.) Location.-On the outer side of the leg. Origin.-Head and upper two-thirds of outer surface of the fibula; the outer tuberosity of the tibia. Insertion.-Under surface of inner cuneiform and base of first metatarsal. Passing back of the outer malleolus, the tendon of insertion, goes forward on the outer side of the calcaneum, and through the groove in the cuboid, diag- onally forward and inward across the sole. Nerve Supply .-Branch of the external popliteal division of the great sciatic. Action.-Extends the foot, raises the outer side and abducts the front. Or extension and eversion, with depression of the great toe. Fig. 158. Soleus and plantaris of right side. (Testut.) THE MUSCLES MOVING THE FOOT 179 Peroneus Brevis. (Figs. 154, 157, 159.) Location.-Lower and outer part of the leg. Origin.--The lower two-thirds of the outer surface of the fibula. Insert ion.-Outer side of the fifth metatarsal, on its tuberosity. Fig. 159.-Tendons in the right sole. (Testut.) Nene Supply . - Branch of the external popliteal division of the great sciatic. Action.-Extends foot, raises the outer side and abducts the front. Or eversion. Note the combined action of the tibialis anterior and posterior in inverting the foot, with their antagonistic action at the ankle-joint; also, that the peroneal muscles combine in everting the foot, though 180 THE MUSCULAR SYSTEM the tertius opposes the other two in its action at the ankle-joint; and, as a group the tibial muscles oppose the peroneals at the medio- tarsal joint. THE MUSCLES MOVING THE TOES. Flexors. *Flexor longus hallucis Flexor brevis hallucis *Flexor longus digitorum Flexor accessorius Flexor brevis digitorum Flexor brevis minimi digiti Lumbricales Extensors. proprius hallucis *Extensor longus digitorum Extensor brevis digitorum * These muscles act on the toes but are in the leg. Abductors. Abductor hallucis Abductor minimi digiti Interossei dorsales Adductors. Adductor obliquus hallucis Adductor transversus hallucis Interossei plantares Flexor Longus Hallucis. (rigs, loo, 159.) Location.-Deep in the back of the leg and in the sole of the foot. Origin.-Lower two-thirds of the posterior surface of the fibula, and adjacent membrane. Insertion.-Under surface of the base of the second phalanx of the great toe. Tendon passes back of the inner malleolus and beneath the sustentaculum tali. Nerve Supply.-- Posterior tibial branch of the great sciatic. Action.-Flexes last phalanx of the great toe. Extends foot at the ankle. Flexor Brevis Hallucis. (Figs. 160, 161.)-Originates from the cuboid and the tendon of the tibialis posterior, passing by two tendons to the two sides of the base of the first phalanx of the great toe, in common with the abductor and adductor of same. Each tendon encloses a sesamoid bone, and in the middle is the tendon of the long flexor of the great toe. The action is to flex the great toe. Flexor Longus Digitorum. (Figs. 155, 159.) Location.-Deep in the back of the leg, and in the sole of the foot. Origin.-Inner part of the posterior surface of the tibia, the middle two-fourths. Insertion.-By four tendons to the base of the third phalanx of the four lesser toes. The tendon of the muscle passes behind the inner malleolus, forward in the sole, and divides into four slips just above the heads of the meta- tarsal bones, and has to go through the perforated slips of the brevis to get to the last phalanx. THE MUSCLES MOVING THE TOES 181 Nerve Supply;-Posterior tibial branch of the great sciatic. Action.-Flexes the last phalanx of the four lesser toes. Extends the foot. Flexor Accessorius. (Fig. 161.)-A muscle originating on the calcaneum, passing forward in the sole to the outer posterior border and upper surface of the above tendon. It flexes the small toes and brings into line with the long axis of the foot, the line of action of the longus digitorum. Fig. 160.-Muscles in the third layer of the right sole. The belly of the flexor brevis minimi digiti has been removed. (Testut.) Flexor Brevis Digitorum. (Fig. 162.) Location.-Sole of the foot. Origin.-Front of the calcaneum. Insertion.-By four tendons to the sides of the second phalanx of the four lesser toes. Nerve Supply.-Internal plantar branch of the great sciatic. Action.-Flexes second phalanx of the four lesser toes. 182 THE MUSCULAR SYSTEM Flexor Brevis Minimi Digiti Pedis. (Fig. 161.)-A small muscle which flexes the first phalanx of the smallest toe. Lumbricales. (Fig. 161.)-Like the lumbricales of the hand, these muscles pass between the flexor and extensor tendons of the toes. They flex the first phalanx and extend the second and third phalanges of the four lesser toes. Fig. 161.-Flexor accessorius and lumbricales of right foot. (Testut.) Fig. 162.-Muscles of the superficial layer of the right foot. (Testut.) Extensor Proprius Hallucis. (Figs. 154, 157.) Location.-In the front of the leg and the dorsum of the foot. Origin.-Middle two-fourths of the fibula, anteriorly and adja- cent membrane. Insertion.-Base of the last phalanx of the great toe, on dorsum. Nerve Supply.-Anterior tibial branch of the great sciatic. Action.-Extends the great toe. Flexes the foot on the leg. THE MUSCLES MOVING THE TOES 183 Extensor Longus Digitorum. (Fig. 154.) Location.-In the front of the leg and dorsum of the foot. Origin.-Outer tuberosity of the tibia; head and upper two- thirds of the fibula, anteriorly; and the adjacent inter- osseous membrane. Insertion.- The tendon divides into four slips, which are inserted into both the second and third phalanges of the four lesser toes. Nene Supply.-Anterior tibial branch of the great sciatic. Action.-Extends the four lesser toes. Flexes the foot at the ankle. Fig. 163.-Extensor brevis digitorum of right foot. (Testut.) Extensor Brevis Digitorum. (Fig. 157.)-A small muscle, entirely in the dorsum of the foot, which is inserted by four tendons into the first phalanx of the great toe, and to the extensor tendon of the longus. Helps to extend the toes. Abductor Hallucis. (Fig. 162.)-Passing from the calcaneum forward, this is inserted into the inner side of the base of the first 184 THE MUSCULAR SYSTEM Fig. 164.-Interossei dorsales of right foot. The line x x is that from which abduction is made. (Testut.) Fig. 165.-Interossei plantares of right foot. The line a: a; is that to which adduction is made. (Testut.) THE MUSCLES OF THE TRUNK 185 phalanx of the great toe, with the inner head of the flexor brevis hallucis. It flexes and abducts the great toe. Abductor Minimi Digiti Pedis. (Figs. 162, 163.)-Passing from the calcaneum forward, this is inserted into the outer side of the little toe, first phalanx. It abducts the little toe. Interossei Dorsales Pedis. (Fig. 164.) Interossei Plantares. (Fig. 165.)-The interossei muscles of the foot serve as adductors and abductors of the toes, to and from the line passing through the second toe, in the same way as in the hand. Two special adductors of the great toe, the oblique and transverse adductors, pass between the great toe and the little toe, helping to preserve the transverse arch of the foot. THE MUSCLES OF THE TRUNK. The muscles of the trunk may be divided into three groups: Those of the back, including some of the neck muscles. Those of the abdomen. Those of the thorax. The muscles of the back compose five layers, none of which are entirely complete. In the first layer, are the trapezius and the latis- simus dor si. In the second layer are the levator scapulae and the rhamboidii major and minor. The Muscles in the Third Layer of the Back. Serratus posterior superior and inferior. Splenius capitis and cervicis. Serratus Posterior Superior. - (O. T. Serratus posticus superior.) (Fig. 166.) Location.-Upper part of the thorax. Origin.-Lower part of the ligamentum nuchae; spinous pro- cesses of the last cervical and two or three upper dorsal. Insertion.-Second to the fifth ribs, beyond the angles. Nerve Supply.-Second and third intercostals. Action.-Raises the upper ribs. Helps to extend the spine, in reversed action. Probably acts in forced inspiration. Serratus Posterior Inferior. - (O. T. Serratus posticus inferior.) (Fig. 124.) Location.-Lower part of the back of the thorax. Origin.-Spinous processes of the two lower dorsal and two upper lumbar vertebrae. Nerve Supply .-Tenth and eleventh intercostal. Action.-Draws down and backward the lower ribs, probably in forced inspiration. 186 THE MUSCULAR SYSTEM Splenius Capitis. -(Fig. 166.) Location.-- The back of the neck, in front of the trapezius. Origin.-Ligamentum nuchae, in the region of third to seventh cervical, and from the spinous processes of the first two to five thoracic vertebrae. Fig. 166.-Muscles in the third layer of the back. The serratus posterior inferior is shown in the next figure. (Testut.) Insertion.-Mastoid process of the temporal and adjacent part of the occipital bone. Nene Supply.-Second, third and fourth cervical nerves. Action.-Inclines and rotates the head and neck toward the side on which muscle is placed. When both sides act, the head and neck are extended. Splenius Cervicis. -(O. T. Splenius colli.) (Fig. 166.) Location.-Lower part of the back of the neck. Origin.-Spinous processes of the third to sixth cervical ver- tebrae. Fig. 167.-Erector spin®, superficial view. (Testut.) Fig. 168.-Erector spin®. The outec series is pulled outward. (Testut.) 188 THE MUSCULAR SYSTEM Insertion.-Posterior tubercles of the first two or three cervical vertebrae. Nene Supply.-Second, third and fourth cervical. Action.-Inclines and rotates the neck toward the side on which the muscle lies. When both act, the neck is extended. The Muscles in the Fourth Layer of the Back. (Figs. 167,168,169.) The muscles in this layer comprise what is known as the erector spince group, extending from the lower end of the spine to the head. It originates as a tendinous sheet, covering the sacral region with the muscle mass filling the space between the iliac crest and the lowest ribs. This mass divides into three divisions, called the inner, outer and middle divisions, which climb the back by relays. The inner division is called the spin- alis dorsi (Fig. 167), and its fibers start from the muscular mass near the middle of the thorax, and are inserted into the spines of the upper thoracic vertebrae, going by steps three or four at a time. The outer division goes from the twelfth rib to the lower part of the neck, while the middle division is car- ried all the way to the head. The outer division (Figs. 167, 169), begins as the iliocostalis, whose muscular slips start from the mass in the lumbar region, and climb up the ribs to the lower six or seven, near their angles. In close association with these, other slips pass upward from the six lower to the six upper ribs, as the musculus accessorius ad iliocostalem, or the accessory muscle of the iliocostalis. The slips have now been carried to the upper margin of the thorax, and a new series of slips relays the erector spinee from the five ribs between the third and seventh, to the transverse processes Fig. 169.-Erector spin®. The middle series is pulled outward. (Testut.) THE MUSCLES OF THE TRUNK 189 of the cervical vertebrae between the fourth and sixth. This is the cervicalis ascendens. The middle division, the longissimus dorsi (Figs. 167, 168, 169), sends slips up the back to the transverse processes of all the lumbar and thoracic vertebrae and to the ribs between the angles and tubercles. These slips vary in length according to the distance gone. (In studying the illustrations, Figs 168 and 169 notice that the muscle slips have been turned inside out by the hooks so as to show the individual attachments.) The longissimus is prolonged upward by the transversalis cervicis or colli. Slips arise from the transverse processes of from four to six upper thoracic vertebrae and are inserted into the transverse processes of the cer- vical vertebrae from the second to the sixth. This division is further prolonged by the trachelo-mastoideus, which arising from the transverse processes of the upper four to six thoracic vertebrae, and the articular processes of the lower three or four cervical vertebrae is carried through the neck to the mastoid process of the temporal bone. The nerve supply of these small divisions comes from the con- tiguous spinal nerves. While the erector spinae as a whole is the length of the back, the subdivisions are not large or long, and as the belly of the muscles is the contracting part, there is a succession of short pulls on the different segments of the spine, making the movements gradual, sustained and powerful. The direct action of the group is the erection or extension of the trunk, with the fixed points at the lower part of the back. If one side acts alone, lateral movement of the trunk to that side is produced. The contractual power of a muscle is measured by its cross-section, so the sum of the cross-sections of these many muscles is equal to one very large one, which would show great power by its size. The Muscles in the Fifth Layer of the Back. These lie in front of the fourth layer and consist of many small slips mostly arising from the transverse processes of the vertebrae, and going to the spinous processes of vertebrae four or five segments ahead. The names of these are: Complexus, or Semispinalis capitis. (Figs. 168, 169.) Semispinalis cervicis. Semispinalis dorsi. Multifidus spince. Rotatores spince. The complexus is the largest muscle of the group, and arises from the transverse processes of the upper six or seven thoracic vertebrae and from the articular processes of the middle three or four cervical, 190 THE MUSCULAR SYSTEM and is inserted into the surface of the occiput between the superior and inferior curved lines. Its action is to extend the head, but if only one side acts, it draws the head to the same side. The semispinalis cervicis and dorsi pass from the transverse pro- cesses of the vertebrae to the spinous processes of those several seg- ments above. They act to extend the neck and spine, but if one side acts alone, the spine is flexed to that side with rotation. The multifidus spince consists of many small slips, which fill the hollow space on each side of the spinous processes, and as their arrangement is essentially the same as the others of this group, the action is the same as the above. The rotatores spines act between the transverse processes of the thoracic vertebrae and the laminae of the same. Their action is to rotate the spine to the opposite side, extend and flex laterally. The nerves supplying these muscles are from the spinal cord in the neighborhood. A group of small muscles, the suboccipital, are more important than their size warrants, as they are seemingly often contracted without the consciousness of a person, producing considerable nervous strain. However, they are under the control of the will. Suboccipital Muscles. (Fig. 169.) Rectus capitis posterior major. Rectus capitis posterior minor. Obliquus capitis inferior. Obliquus capitis superior. These four muscles are deeply placed under the overhang of the occiput, and pass from the axis and atlas to the occiput. Their actions are to extend the head and rotate it, directly or by rotating the atlas carrying the head. The suboccipital nerve supplies these muscles, but their involun- tary constant contraction interferes with the functioning of the sympathetic fibers in the region. THE MUSCLES OF THE ABDOMEN. Rectus abdominis Pyramidalis Obliquus externus abdominis Obliquus interims abdominis Transversalis abdominis Quadratus lumborum The abdominal cavity is covered in by these six muscles, which are arranged in three layers. In the male subject, it is usually possible to separate the layers and see distinct thickness in them. In the female subject, on the dissecting table, it is frequently diffi- cult to distinguish the separate layers, because the entire covering is so thin on account of lack of development of the muscles. THE MUSCLES OF THE ABDOMEN 191 Rectus Abdominis. (Fig. 170.) Location.- In the front wall of the abdomen near the middle. Origin.-The crest and symphysis of the os pubis. Insertion. -The cartilages of the fifth, sixth and seventh ribs. Nerve Supply.-Lower intercostal and iliohypogastric. Action.-Flexes the spine, if one side is used; depresses the thorax; compresses the abdominal viscera; when thorax.is fixed, it flexes the pelvis on the trunk. Fig. 170.-Rectus abdominis and obliquus internus of right side. (Testut.) Fig. 171.-Obliquus externus abdominis of right side. (Testut.) Pyramidalis.-An adjunct to the rectus, not always present. It passes from the pubic ramus to the lower part of the linea alba. It draws down the linea alba in the middle line. Same nerve supply as the rectus. Obliquus Externus Abdominis. (Fig. 171.) Location.- Superficial in the lateral wall of the abdomen. Origin.-By eight fleshy digitations from the eight lower ribs beyond the cartilages. First five interdigitate with the serratus magnus, the other three with the latissimus dorsi. 192 THE MUSCULAR SYSTEM Insertion.--The anterior half of the outer lip of the crest of the ilium; Poupart's ligament; and the linea alba. Nerve Supply.- Lower intercostals, ilioinguinal and iliohypo- gastric. Action.-Compresses the abdominal viscera; depresses the thorax; flexes the spine; rotates the trunk to the opposite side, when only one side acts; with the thorax fixed, it flexes and rotates the pelvis to the same side. Poupart's ligament is not a true ligament, but is the lower border of the obliquus externus abdominis between the anterior-superior spine of the ilium and the pubic tubercle. The muscle is covered by fascia, which folds under and forms a shelf-like structure, to which other muscles are attached. This is also called the inguinal ligament. Fig. 172.--Semidiagrammatic horizontal section of trunk to show the lumbar fascia and the tendons of the lateral abdominal muscles. The upper figure shows the complete sheathing of the rectus in its superior portions; the lower shows the arrangement in its inferior fourth. (Testut.) » The tendon of insertion of the obliquus externus, interims and the transversalis is a sheath of fibrous tissue, that is in layers. On the outer side is that from the externus which passes in front of the rectus, covering it, joined to the outer half of the internus apo- neurosis, and interlacing with the fibers from the other side of the abdomen to form a dense fibrous band, the "white line" or linea alba. The posterior half of the aponeurosis of the internus and that from the transversalis passes to the rear of the rectus, and THE MUSCLES OF THE ABDOMEN 193 forms the posterior part of its sheath, then joins the other fibers to form the linea alba. The aponeurosis of the externus at the lower part, just above the body of the pubis, presents diverging fibers that form an opening, the external abdominal ring, the outer opening of the inguinal canal. (See text-books that go into more details.) Fig. 173.-Transversalis abdominis of right side. (Testut.) Obliquus Internus Abdominis. (Figs. 170 and 172.) Location.-In the second layer on the lateral wall of the abdo- men. Origin.- Outer half of Poupart's ligament; the middle lip of the anterior two-thirds of the crest of the ilium, and the lumbar fascia. Insertion.-Lower border of the cartilages of the six lower ribs; ensiform process; linea alba; crest of the os pubis and ilio- pectineal line. Nerve Supply.- Lower intercostals, ilioinguinal and iliohypo- gastric. 194 THE MUSCULAR SYSTEM Action.-Depresses the thorax; compresses the abdominal viscera; flexes the spine; side bend and rotate to same side, when only one side acts; and when thorax is fixed, flexes and rotates the pelvis to the opposite side. Transversalis Abdominis. (Fig. 173.) Location.-Deep in the lateral wall of the abdomen. Origin.-Inner side of the cartilages of the six lower ribs; inner lip of the iliac crest; lateral half of Poupart's ligament and the lumbar fascia. Insertion.-Linea alba; iliopectineal line and crest of the pubis, by the conjoined tendon of itself and that of the internus. Nene Supply.-Lower intercostals, ilioinguinal and iliohypo- gastric. Action.- Mainly to compress the abdominal viscera. May aid in expiration by contracting the thorax. Quadratus Lumborum. (Fig. 143.) Location.-Deep in the posterior wall of the abdomen. Origin.-Inner lip of the iliac crest; transverse processes of three or four lumbar vertebrae; iliolumbar ligament and lumbodorsal fascia. Insertion.- Last rib; transverse processes of three or four lumbar vertebrae. Nene Supply.-Fir st three or four lumbar. Action.-Lateral flexion of the spine; both acting together, extends spine; depresses and flexes the twelfth rib, in forced expiration. THE MUSCLES OF THE THORAX. Diaphragm Intercostales externi Intercostales interni Levatores costarem Triangularis sterni Subcostales Diaphragm. (Fig. 174.) Location.--Between the thoracic and abdominal cavities. Origin.-From the front of the bodies of the upper two lumbar vertebrae (four vertebrae on the right side), and the inter- vertebral disks, two crura are formed which arch over from one side to the other, and form an opening through which passes the aorta. The ligamentum arcuatum internum, forms a fibrous band which passes from the body of the first lumbar ver- tebra to the tip of its transverse process, while the liga- mentum arcuatum externum passes from the tip of the transverse process to the last rib. These arch over the psoas magnus and the quadratus lumborum, respec- THE MUSCLES OF THE THORAX 195 tively. Inner surface of the cartilages of the six lower ribs, interdigitating with the transversalis, and to the ensiform process. Insertion.-The muscle fibers converge to a central, three- leaved tendon. Nene Supply.-The phrenic, from the cervical plexus. Action.-Flattens the arch, so increasing the vertical diameter of the thorax, by which means inspiration follows. It is the principal muscle of inspiration. Exerts pressure upon the abdominal organs if the front abdominal wall is not flaccid. Muscles which act at the same time as the dia- phragm in respiration are classed as inspiratory muscles. Fig. 174.-Diaphragm, viewed from in front. (Testnt.) Intercostales externi are on the outer wall of the thorax, passing between the ribs, while the intercostales interni are on the inner wall, filling in the spaces between the ribs. The externi raise the ribs, and are assisted by the levatores costarum, possibly, but the action of the interni is not agreed upon. (Fig. 125.) The Levatores costarum pass between the transverse processes of the thoracic vertebrae to the dorsal surface of the rib below. 196 THE MUSCULAR SYSTEM Triangularis sterni is a small triangular shaped muscle on the inner side of the thoracic wall in front. It depresses the ribs to whose cartilages it is attached. Fig. 175.-Deep lateral and prevertebral muscles of the neck. (Testut.) Subcostales are small muscles, near the angle of the ribs, on the inner surface of the thorax. Their action is not well determined. The nerve supply of the above group of muscles are the respective intercostal nerves in their vicinity. Although not on the thorax, several other muscles which have to do with respiration may be considered here. Located on the side of the neck, they act upon the upper ribs. Scalenus Anterior. -((). T. Scalenus anticus.) (Fig. 175.) Origi- nating from the anterior tubercles of the transverse processes of the third to the sixth cervical vertebrae, the fibers are inserted on the THE MUSCLES OF THE THORAX 197 upper surface of the first rib. Its action is to elevate that rib, and with the other two scaleni provide a basis for the intercostals to act in inspiratory lifting of the chest. Scalenus Medius. (Fig. 175.)-An origin from the transverse processes of all the cervical vertebrae, and insertion into the upper surface of the first rib, gives this muscle the same action as the preceding. Fig. 176.-Muscles in front and side of neck. (Testut.) Scalenus Posterior. -(O. T. Scalenus posticus.) (Fgs. 173, 174.) Coming from the transverse processes of the lower two or three cervical vertebrae, it is inserted into the outer surface of the second rib in front of the angle. Action, a part of the group as above. The nerve supply of the group is from the cervical nerves in the vicinity. 198 THE MUSCULAR SYSTEM THE MUSCLES OF THE HEAD AND NECK. Stemo-cleido-mastoideus. (Fig. 175.) Location.-Superficial on the front and side of the neck. Origin.- The inner third of the upper border of the clavicle, and the upper border of the sternum. Insertion.- Mastoid process of the temporal bone; outer half of the superior curved line of the occipital bone. Nerve Supply.- Spinal accessory and second cervical. Action. -When one side acts, it draws the head to the side, and turns the face to the opposite side. When both mus- cles act, they extend the head. Platysma. (Fig. 177.)-A thin sheet of fibers passing between the clavicle and the chin, drawing down the angle of the mouth and the lower lip, and contracting the skin of the neck. A group of muscles, some above, some below the hyoid bone, and connecting the latter with the lower jaw or the upper part of the thorax, need be mentioned only. Their function has largely to do with deglutition. Digastricus. (Fig. 176) Stylohyoideus. (Fig. 176) Mylohyoideus. (Fig. 176) Geniohyoideus. Sternohyoideus. (Fig. 176) Omohyoideus. (Fig. 176) Sternothyroideus. (Fig. 176) Thyrohyoideus. A group of muscles, deep in the front of the neck, of which the first bends the neck sideways, and the others flex it forward, are, Rectus capitis lateralis. (Fig. 175) Rectus capitis anterior major. (Fig. 175) Rectus capitis anterior minor. (Fig. 175) Longus colli. (Fig. 175) The last group of muscles to be considered are those of expression and of mastication. They are superficial on the head, and a study of the illustrations with their names will be sufficient. Muscles of Expression.-All supplied by the facial nerve. Tho'se affecting the orifice of the mouth. Orbicularis oris. (Fig. 177) Levator labii superioris alceque nasi. (Fig. 177) Levator labii superioris proprius. (Fig. 177) Zygomaticus minor. (Fig. 177) Zygomaticus major. (Fig. 177) Levator anguli oris. (Fig. 177) Risorius. (Fig. 177) 199 THE MUSCLES OF THE HEAD AND NECK Fig. 177.-Superficial muscles of head and neck. (Testut.) 200 THE MUSCULAR SYSTEM Buccinator. (Fig. 176) Depressor anguli oris. (Fig. 177) Depressor labii inferioris. (Fig. 177) Levator labii inferioris. (Fig. 177) Those of the nose. Pyramidalis nasi. (Fig. 177) Compressor naris. (Fig. 176) Levator labii superioris aloeque nasi. (Fig. 177) Depressor aloe nasi. Those of the eyelids. Orbicularis palpebrarum. (Fig. 177) Tensor tarsi Levator palpebrce Those of the forehead. Corrugator supercilii Frontalis. (Fig. 177) Of the occiput. Occipitalis. (Fig. 176) Muscles of Mastication.-Supplied by the trifacial or fifth cranial nerve. Masseter. (Figs. 176, 177) Pterygoideus internus Temporalis. Pterygoideus externus GROUPING OF MUSCLES ACCORDING TO FUNCTION. (Based Upon Morris' Human Anatomy.) In the following table only the principal muscles are considered, omitting those given but brief mention. Muscles Acting on the Head. To Flex It.- The supra- and infrahyoid muscles; rectus capitis anterior major and minor. To Extend It.-Sterno-cleido-mastoideus, trapezius, splenius capitis, trachelo-mastoideus, complexus, obliquus capitis superior, rectus capitis superior major and minor. To Bend to Side.-Sterno-cleido-mastoideus, rectus capitis lateralis, splenius capitis, trachelo-mastoideus, complexus, obliquus capitis superior. To Rotate It.- Sterno-cleido-mastoideus, trapezius, splenius capitis, trachelo-mastoideus, complexus, obliquus capitis superior and inferior, rectus capitis superior major and minor. Muscles Acting on the Spinal Column. To Flex It-Sterno-cleido-mastoideus, longus colli, rectus capitis anterior major, psoas magnus, scaleni, rectus abdominis, obliquus externus and internus abdominis. GROUPING OF MUSCLES ACCORDING TO FUNCTION 201 To Extend It.-Splenius capitis, splenitis cervicis, erector spime, semispinalis dorsi and cervicis, complexus, multi- fidus, rotatores, interspinales, levatores costarum and quadratus lumborum. To Bend It Laterally and Rotate.-Sterno-cleido-mastoideus, scaleni, longus colli, trapezius, levator scapulae, splenius capitis and cervicis, semispinalis dorsi, and cervicis, com- plexus, multifidus, rotatores, intertransversales, levatores costarum, psoas magnus, quadratus lumborum, obliquus externus and internus abdominis, rectus abdominis. Muscles of Respiration. Quiet Inspiration.-External intercostals, anterior internal intercostals, diaphragm. Forced Inspiration.-The above, and the scaleni, sterno-cleido- mastoideus, serratus posterior-superior and inferior, rhom- boids, serratus magnus, latissimus dorsi, pectoralis major and minor, and the extensors of the spinal column. Quiet Expiration.-Posterior part of internal intercostals, subcostales, triangularis sterni. Forced Expiration.-The above and the abdominal muscles, erector spinae, and quadratus lumborum. Muscles Acting on the Shoulder-girdle. Elevation. - Levator scapulae, trapezius, sterno-cleido-mas- toideus, rhomboidei, serratus magnus, omo-hyoideus. Depression.- Trapezius (lower part) pectoralis major (lower part) pectoralis minor, subclavius, latissimus dorsi. Abduction.-Serratus magnus, pectoralis major and minor. Adduction.-Trapezius, rhomboidei, latissimus dorsi. Rotation, uith Abduction of A rm.-Serratus magnus (lower part), trapezius, upper part, levator scapulae. Rotation with Adduction of Arm. - Rhomboidei, trapezius (lower part), serratus magnus (upper part), pectoralis major (lower part), and latissimus dorsi. Muscles Acting on the Arm at the Shoulder-joint. Abduction. - Deltoideus, supraspinatus, biceps (long head), pectoralis major. Adduction.-Pectoralis major, latissimus dorsi, teres major, coraco-brachialis, long head of triceps. Flexion.-Pectoralis major, deltoideus (clavicular portion), subscapularis, coraco-brachialis, biceps (short head), and serratus magnus. Extension.-Deltoideus (posterior part), teres major, latis- simus dorsi. Outward Rotation.-Infraspinatus, teres minor. Inward Rotation.-Subscapularis, deltoideus (anterior part), teres major, latissimus dorsi, and pectoralis major. Muscles of Respiration. 202 THE MUSCULAR SYSTEM Muscles Acting on the Forearm. Flexion (Forearm Supinated.) -Brachialis, biceps (long head), brachio-radialis, biceps (short head), extensor carpi radialis longus, pronator teres, flexor carpi radialis, extensor carpi radialis brevis, palmaris longus. Flexion (Forearm Pronated or in Mid-position.) - Brachialis, brachio-radialis, biceps, extensor carpi radialis longus and brevis, pronator teres, flexor carpi radialis and palmaris longus. Extension.-Triceps and anconeus. Pronation of Forearm (Forearm Extended.)-Pronator teres, flexor carpi radialis, pronator quadratus, palmaris longus. Pronation of Forearm (Forearm at Rigid Angles.)- Pronator teres, brachio-radialis, flexor carpi radialis, pronator quadratus, extensor carpi radialis longus and palmaris longus. Pronation of Forearm (Forearm Flexed.)-Pronator teres and quadratus, brachio-radialis, flexor carpi radialis, extensor carpi radialis longus, and palmaris longus. Supination of Forearm (Forearm Extended).-Brachio-radialis, biceps, supinator, extensor carpi radialis longus, abductor pollicis longus, extensor pollicis brevis and longus, extensor indices. Supination of Forearm (Forearm Flexed.)-Biceps, supinator, extensor longus and brevis pollicis, extensor indicis, abductor pollicis longus (extensor ossis metacarpi pollicis). Muscles Acting on the Hand at the Wrist. Flexion.-Flexor carpi radialis and ulnaris, palmaris longus, the long flexors of the fingers and thumb. Extension.-Extensor carpi radialis longus and brevis, extensor carpi ulnaris, and the extensors of the fingers and thumb. Abduction.-Extensor carpi radialis longus and brevis, extensor ossis metacarpi pollicis, extensor brevis pollicis, flexor carpi radialis. Adduction.-Flexor carpi ulnaris, extensor carpi ulnaris. Muscles Acting on the Fingers. Flexes All the Joints.-Flexor profundus digitorum. Flexes All But the Last.-Flexor sublimis digitorum. Flexes the First Only .-Plexor minimi digiti, lumbricales and interossei. Extends the Fingers.-Extensor communis digitorum, extensor indicis, extensor minimi digiti. Muscles Acting on the Thumb. Flexes All Joints.-Flexor longus pollicis. The carpo-meta- carpal joint, extensor ossis metacarpi pollicis, opponens pollicis. Extends All Jow/.v.-Extensor longus pollicis. GROUPING OF MUSCLES ACCORDING TO FUNCTION 203 Muscles Acting on the Pelvis. Flexion.-Rectus abdominis, obliquus internus and externus abdominis, psoas magnus. Extension.-Erector spin® and multifidus. Lateral Flexion with Rotation.-Rectus abdominis, obliquus internus and externus abdominis, qjuadratus lumborum, and psoas magnus acting on one side only. Muscles Acting on the Thigh at the Hip-joint. Flexion.-Iliopsoas, sartorius, rectus femoris, pectineus, gra- cilis, adductor longus and brevis, tensor fasciae latse. Extension. - Gluteus maximus, biceps, semitendinosus, semi- membranosus, adductor magnus. Adduction.-Gracilis, pectineus, adductors magnus, longus and brevis, quadratus femoris, obturator externus, and lower part of gluteus maximus. Abduction.-Gluteus medius and minimus, tensor fasciae latae, gluteus maximus, and when hip is flexed, pyriformis, obturator internus and gemelli. Inward Rotation.-Tensor fasciae latae, gluteus medius and minimus, iliopsoas. Outward Rotation. -Pyr'dormis, obturator externus and inter- nus, gemelli, quadratus femoris, gluteus maximus and medius, sartorius, pectineus, adductor longus, brevis and magnus, biceps. Muscles Acting on the Leg at the Knee-joint. Flexion.-Sartorius, gracilis, semitendinosis, semimembranosus, biceps, gastrocnemius, popliteus. Extension.-Quadriceps extensor cruris. Inward Rotation (When Flexed.)-Sartorius, gracilis, semi- tendinosis, semimembranosus, popliteus. Outward Rotation (When Flexed.) - Biceps femoris. Muscles Acting on the Foot at the Ankle-joint. Flexion.- Tibialis anterior, extensor longus digitorum, extensor longus hallucis, peroneus tertius. Extension.-Soleus, gastrocnemius, flexor longus hallucis, peroneus longus and brevis, tibialis posterior, flexor longus digitorum. Inversion at Medio-tarsal Joint.-Tibialis posterior and anterior. Eversion at Medio-tarsal Joint. - Peroneus longus brevis and tertius. Note.-The exact function of many muscles has not been deter- mined decisively. What a muscle should do according to the law of mechanics is not always conclusive of what it really does, influ- enced by the action of antagonistic and fixator muscles. 204 THE MUSCULAR SYSTEM Fig. 178.-The right upper limb ab- ducted and supinated, viewed from in front. (Gerrish.) Fig. 179.-Key to Fig. 178. (Gerrish.) SURFACE ANATOMY 205 Fig. 180.-The right upper limb abducted and pronated, viewed from in front. (Gerrish.) Fig. 181.-Key to Fig. 180. (Gerrish.) 206 THE MUSCULAR SYSTEM Fig. 182.-The right upper limb, ab- ducted and supinated, viewed from behind. (Gerrish.) Fig. 183.-Key to Fig. 182. (Gerrish.) 207 SURFACE ANATOMY Fig. 184.-The right upper limb, abducted and pronated, viewed from behind. (Gerrish.) Fig. 185.-Key to Fig. 184. (Gerrish.) Fig. 186.-The right lower limb, front view. (Gerrish.) Fig. 187.-Key to Fig. 186. (Gerrish.) Fig. 188.-The right lower limb, rear view. (Gerrish.) Fig. 189.-Key to Fig. 188. (Gerrish.) 210 THE MUSCULAR SYSTEM Fig. 190.-The right lower limb, external lateral view. (Gerrish.) Fig. 191.-Key to Fig. 190. (Gerrish.) SURFACE ANATOMY 211 Most of the muscles are placed in pairs, symmetrically on the of the body, and the few that are described as single, have two sides. Some muscles are not constantly present, and in every cadaver something is likely to be lacking. Fig. 192.-The right lower limb, in- ternal lateral view. (Gerrish.) Fig. 193.-Key to Fig. 192. (Gerrish.) The number of muscles of the body, according to the differences in description, is given by varying authors as 400 to 622. Less then 100 pairs have been presented here as necessary for the student in physical education to really study and know. Fig. 194.-Comparison of shoulders and arms in different attitudes. The sliding outward of the scapula when the arm is raised is very marked. (Gerrish.) QUESTIONS. What muscles connect the head with the scapula? What muscles connect the arm with the ribs? What muscles connect the pelvis with the arm? Name the flexors of the forearm. Name the extensors of the thumb and fingers. What muscles adduct the hand? Name some muscles that pass over two joints. What muscles extend the leg upon the thigh? Name the adductor muscles of the thigh. Which muscles extend one joint and flex the joint below? Name the muscles that supinate the foot. What is the action of the gluteus maximus? On which surface of the tibia do the flexors of the foot find attachment? Name the divisions of the erector spinse, with a general description of the muscles. What muscles form the abdominal wall? Describe the diaphragm. Compare the functions of the muscles of the upper extremity with those of the lower extremity. CHAPTER VI. GENERAL CONSIDERATION OF Bl'RS.F. THE'small synovial sacs which are called burste are very numerous, but it is unnecessary to consider more than a limited number of them. In certain locations, bursse are always found, because they are needed to enable the muscle or tendon under which they are placed to function smoothly. Where an occupation causes an excessive amount of pressure over bone, bursae may be developed in self-defense, as with cobblers who hold a stone on the thighs and pound their leather on it. The bursa develops between the rectus femoris and the vasti muscles. Or, as they hold the shoe against their breast-bone, there is a new bursa formed. Persons who carry heavy burdens on their shoulders develop a bursa over the spine of the scapula, wThere the pressure is most marked. The bursse considered here are those in relation to the shoulder- elbow-, knee- and ankle-joints. BURSJE IN RELATION WITH THE SHOULDER-JOINT. The bursa trapezii, is located between the trapezius muscle and the triangular space at the root of the spine of the scapula. The bursa acromialis subcutanea, is placed between the acromion process and the skin over it. The bursa subacromialis is between the capsular ligament of the shoulder-joint and the arch made by the coracoid and acromial processes, and extends beneath the deltoideus muscle. This is some- times called the bursa subdeltoidea. This bursa is very liable to injury and inflammation, producing marked impairment in the use of the arm. BURSAS IN RELATION WITH THE ELBOW-JOINT. The bursa bicipito-radialis, is placed between the tuberosity of the radius and the tendon of the biceps muscle. The bursa olecrani subcutanea, is between the dorsal surface of the olecranon and the overlying skin. 213 214 GENERAL CONSIDERATION OF BURSA? BURSAS IN RELATION WITH THE KNEE-JOINT. A large number of bursae exist about the knee-joint, of which the following should be noted. The bursa sartorii is placed between the sartorius muscle and the inner tuberosity of the tibia, separating the tendon of the sartorius from those of the gracilis and semitendinosus muscles. The bursa semimembranosus is between the tendon of the semi- membranosus muscle and the inner tuberosity of the tibia. The bursa tibialis interna is placed between the internal lateral ligament of the knee-joint and the tendons of the inner hamstrings; sartorius, gracilis and semitendinosus muscles. The bursa bicipitis cruris is between the external lateral ligament of the knee-joint and the tendon of the biceps femoris muscle. The bursa poplitei is placed between the origin of the popliteus muscle on the external condyle of the femur and the external tuber- osity of the tibia and the capsular ligament of the knee-joint. The bursa suprapatellaris is between the quadriceps extensor cruris muscle and the lowTer part of the shaft of the anterior surface of the femur. The bursa prepatellaris subcutanea is located between the skin and the anterior surface of the patella. The bursa infrapatellaris is placed between the ligamentum patellae and the anterior surface of the upper part of the tibia. The bursa condyli externi is between the external condyle of the femur and the skin. The bursa condyli interni is between the internal condyle of the femur and the skin. The bursa pretibialis is between the tubercle of the tibia and the overlying fascia. BURS7E IN RELATION WITH THE ANKLE-JOINT. The bursa postcalcanea profunda, lies between the posterior sur- face of the os calcis and the tendo Achillis. The bursa malleoli externi subcutanea is placed between the external malleolus and the skin. The bursa malleoli interni subcutanea is between the internal malleolus and the skin. THE FASCIAL Fasciae are fibrous sheets which are wrapped around various organs, especially muscles, serving to keep them in definite and intimate relation with each other. The term also includes certain strong fibers that connect bony parts. The fasciae include two varieties, superficial and deep. The THE FASCIAE 215 typical superficial fascia is the continuous layer of areolar tissue directly under the skin, connecting and separating the skin from the deeper structures, including the deep fascia. It contains fat cells, forms a bed for bloodvessels and nerves on their way to and from various organs. There is much variation in the thickness of this superficial fascia from a very thin and delicate membrane to the big-meshed and heavy structure. Over the abdomen and the but- tocks the meshes are large, frequently holding an enormous accu- mulation of fat cells, even several inches thick. Except on the palms and soles which are held firmly, the superficial fascia allows the skin to move with considerable freedom. The deep fasciae are strong, close sheets of white fibrous tissue. They appear as iridescent, pearly-white structures, very flexible and non-elastic. Sometimes they are really the spread-out tendon of a muscle. At times they serve as ligaments, and are generally in close association with other forms of fibrous tissue as tendons, periosteum, etc. While they sheath muscles, they also pass between as septa and connect them. While all the muscles are covered by fascia, in certain localities there is a thickening and accentuation of it. In the upper extremity at the wrist are transverse bands of fibers which are called annular ligaments, anterior and posterior respectively. They hold the tendons in place, keeping them from flying out, as they pass from the forearm into the hand. See Figs. 133, 136, pages 147, 151. On the palm of the hand the palmar fascia is particularly strong and dense. It is sometimes an expansion of the tendon of the palmaris longus. It gives protection to the nerves and bloodvessels in the palm and adds much to the strength of the "grip." The lumbar fascia is essentially a combination of spread-out tendons, though it also covers some muscles as a sheath. Fig. 172, page 192. The tendons of the latissimus dorsi, serratus posterior inferior, obliquus internus abdominis and transversalis abdominis muscles help to form this fascia, though they are frequently described as arising from it. It is attached to the spines and transverse pro- cesses of the lumbar and sacral vertebrae, to the last rib and to the outer lip of the posterior third of the crest of the ilium. It forms three layers, and invests as a sheath the quadratus lumborum and erector spinae muscles, besides giving attachment to them. The Fascia Lata.-The fascia lata is a very strong and dense sheath covering the entire musculature of the thigh, and sending some fibers to help make the capsular ligament of the knee-joint. It is a single layer in most of its extent, but splits so as to encase the gluteus maximus and the tensor fascia lata muscles. It is more dense on the outer aspect of the thigh. The contraction of the tensor fasciae latae tightens this fascia and adds much to the efficiency of the other muscles of the thigh. 216 GENERAL CONSIDERATION OF BURSA? Annular Ligaments of the Ankle.-At the ankle, transverse bands of fibers form an annular ligament to hold the tendons which pass into the foot from flying out when their muscles contract. There are three divisions of the ligament, anterior, internal and external. Fig. 195.-The anterior annular ligament of the ankle and the synovial tnembranes of the tendons beneath it artificially distended. (Testut.) The anterior annular ligament holds down the tendons of the extensor longus digitorum, peroneus tertius, tibialis anterior, and extensor proprius hallucis muscles (Fig. 195). THE FASCIAE 217 The internal annular ligament holds down the tendons of tibialis posterior, flexor longus digitorum and flexor longus hallucis muscles (Fig. 196). Fig. 196.-The internal annular ligament of the ankle and the artificially distended synovial membranes of the tendons which it confines. (Testut.) Fig. 197.-The external annular ligament of the ankle and the artificially distended synovial membrane of the tendons which it confines. (Testut.) The external annular ligament holds down the tendons of the peroneus longus and peroneus brevis muscles (Fig. 197). 218 GENERAL CONSIDERATION OF BURS Al Plantar Fascia.-On the sole of the foot where the bloodvessels and nerves are peculiarly susceptible to injury in walking, the layer of fascia is very dense and thick. Transverse bands hold in place the tendons which move the toes. Connection of Fasciae and Veins.-In most of the joints of the body, but especially at the shoulder, lower part of the neck, the elbow-, knee- and hip-joints, the deep fascia is attached to the fibrous cov- ering of the large veins in those regions. When the joint is moved, the fascia is pulled and in turn it pulls upon the veins, opening out the latter and creating a partial vacuum. This is instantly filled by the rush of blood and thus serves as a suction pump in returning the venous blood to the heart, as it cannot go in the opposite direction on account of the valves. When the pull is released, the veins return to their former caliber, and this presses upon the blood, sending it along toward the heart. Thus the deep fasciae serves an important use in the circulation of the blood. QUESTIONS. What is a bursa? Where are bursae placed? What results from an inflammation of the bursa subacromialis? What joint needs and has the greatest number of bursae? What is the "fascia lata?" What is the "annular" ligament of the wrist? What would probably result if there was no "annular" ligament of the ankle? CHAPTER VII. THE NERVOUS SYSTEM. The nervous system is divided into two parts, the cerebrospinal and the sympathetic or autonomic. The cerebrospinal system is the seat of conscious knowledge, of will, of coordination, of thought and of sensation. With this part of the nervous system we see, hear, taste, smell, feel, think. After assembling these sensations we make such responses by motion as the will ordains. Or, we even respond by motion without the will being concerned. All the so-called higher faculties are lodged in the cerebrospinal axis. Anatomically the cerebrospinal system consists of the cerebro- spinal axis, the cranial and spinal nerves. The cerebrospinal axis consists of the brain or encephalon, and the spinal cord. GENERAL CONSIDERATIONS OF THE BRAIN, INCLUDING SOME SPECIAL CENTERS. The Encephalon.-The encephalon is contained in the cranial cavity, and weighs on an average about three pounds. It consists of four parts, the cerebrum, the cerebellum, the pons varolii, and the medulla oblongata. The spinal cord hangs within the spinal canal. The brain is covered by three membranes, the pia mater, the dura mater and the arachnoid. These are called the meninges. The pia is next to the brain substance, and is a very delicate network of small bloodvessels, supported by areolar tissue, carrying nutrition to the various parts of the surface. It dips down into the various fissures. The dura is a dense strong fibrous structure in two layers, which not only covers the brain, but serves as the periosteum of the cranial bones. These layers are closely united except in certain places. Small channels in the cranium are lined by the dura, and shelf-like processes project toward each other so that canals are formed which contain veins. These are call sinuses. (Fig. 198.) Prolongations of the dura serve to separate parts of the brain. The tentorium is that between the cerebellum and the occipital portion of the cerebrum; the falx cerebri is between the two hemispheres and the falx cerebelli separates the cerebellar hemispheres. 219 220 THE NERVOUS SYSTEM On the inner surface of the dura is a delicate layer of epithelial cells, with a similar layer on the outer surface of the pia. These form the arachnoid membrane, essentially a serous membrane and secreting a fluid, the cerebrospinal fluid. This fluid forms a water-bed between the brain and the bones of the cranium, lessening jar. The brain is never completely at rest, and it is literally churned up and down by the varying amounts of blood going to it. The respiratory movements, and the pulsations Fig. 198.-Sinuses of the dura, left lateral view. (Testut.) of the large arteries of the brain vary in force and frequency, some- times being very rapid and strong. The jarring effects of these are minimized by the water-bed. This fluid is also found in the spinal canal, protecting the cord. Much of the fluid is found in hollow spaces in the center of the brain, which are called ventricles. Five such spaces exist and com- municate with each other and with the spinal canal. The varying amount of blood in the brain may be observed by watching the fontanelles on the head of an infant. Every time the GENERAL CONSIDERATIONS OF THE BRAIN 221 child inspires, the skin covering the fontanelles sinks in, while during expiration there is a bulging out. The four divisions of the brain vary much in size. Largest of all is the cerebrum, or fore-brain, extending from the forehead to the occiput and filling the vault of the cranium above the eyes and ears. It is divided into right and left hemispheres. The cerebrum rests upon the floor of the cranium, leaving but a small compartment for the rest of the brain. Fig. 199.-Semidiagrammatic view of the cerebrospinal axis, left side. (Testut.) The tentorium forms a tent over the cerebellum and keeps the pressure of the posterior lobes of the cerebrum from it. The second division in size is the cerebellum, or hind-brain. It occupies the back part of the base of the skull. (Fig. 199.) The pons varolii surmounts the medulla and is the means by which the medulla is connected with the cerebrum and cerebellum. It is the cross-roads of the brain, resting on the base of the cranium just in front of the medulla. The medulla oblongata is virtually the upper end of the spinal cord expanded into a club-shaped process, and projected into the cranial cavity, resting on the base of the skull for about 222 THE NERVOUS SYSTEM 1| inches. Its upper portion forms the floor of the ventricular space. The Cortex.-The tissue of the brain is divided into gray and white matter, the gray matter representing the cellular or working ele- ment, and the white matter the communicating fibers. The gray matter is on the outside of the brain, forming a layer about | inch thick, called the cortex. Fig. 200.-Brain of six-months' human embryo, natural size, right side. (Kblliker.) This is an aggregation of neurons, with the axones leading out of the brain to some part of the periphery but with the branching processes in intimate association with their neighbors. As animals ascend in the scale of intelligence and brain power there is a change in the appearance of this layer of gray matter. This is illustrated by the human fetus, which at six months shows a perfectly smooth Fig. 201.-Cerebrum of eight-months' human embryo, left side. The insula is nearly covered in. (Testut.) layer of gray matter in the cortex (Fig. 200), but shortly begins to show wrinkling and folds all over it. The wrinkles become deeper and more numerous as the brain develops and are called fissures. (Fig. 201.) Individuals are more able, not according to the size of their brains, but according to the depth and number of the wrinklings and in the multitude of their associations. GENERAL CONSIDERATIONS OF THE BRAIN 223 This arrangement gives space for a vastly greater number of neu- rons than could be accommodated on a smooth surface. The fissures vary on the two sides of the brain and in different individuals, but correspond very constantly. (Fig. 202.) The space between the fissures is called gyrus or convolution, and every one is named. The longitudinal fissure divides the cerebrum into lateral halves. The Sylvian fissure starts near the center of the base of the brain, going upward and backward, then dividing into anterior and poste- rior limbs. Above the Sylvian fissure in the middle region of the lateral surface is the fissure of Rolando, or the central fissure. It starts from the longitudinal fissure and passes downward almost to the Sylvian fissure. Fig. 202.-The gyri and fissures of the external lobes of the left hemisphere. (Gerrish.) The parieto-occipital fissure begins far back on the upper margin of the hemisphere and continues downward and forward. These fissures mark, more or less accurately, the boundaries of four lobes of the brain, the frontal, parietal, temporal and occipital. (Fig. 203.) A fifth lobe, the insula is scarcely visible from the surface, because the other lobes develop so much faster they cover it from sight. A sixth lobe is the limbic or falciform. (Fig. 204.) These lobes form the major divisions of the cerebrum, the gyri form the divisions of the lobes, while larger or smaller fissures respectively separate them. 224 THE NERVOUS SYSTEM The Corpus Callosum.-Beneath the gray matter in the cerebrum is a large mass of white matter, the corpus callosum. It consists of Fig. 203.-The lobes of the convex surface of the hemisphere, left side. (Gerrish.) medullated fibers which cross from one side of the brain to the other, from one part of a hemisphere to another part. (Fig. 205.) Fig. 204.-The lobes of the mesial and tentorial surfaces of the left hemisphere. (Gerrish.) It is like a great flat band of nerve fibers which runs from side to side forming the roof of the ventricular space. By means of these, GENERAL CONSIDERATIONS OF THE BRAIN 225 the gray matter of one part of the cerebrum is held in close and constant communication with the gray matter of every other part. The fibers run in every direction, the arrangement being very intri- cate. Impressions received from the outer world are coordinated with thought, emotion and motor activity. Every voluntary movement of the body is a complex act. It is preceded or accompanied by certain sensations or perceptions which occur in some part of the brain, dependent upon stimulation of the sensory nerves in some way, or upon experience derived from former Fig. 205.-Coronal section of the hemispheres through the middle commissure: Amyg. Nuc., amygdaloid nucleus; C.N., caudate nucleus in the roof of the middle horn of the right lateral ventricle; Corp. Alb., corpora albicantia; Ext. Caps., external capsule; Forn., fornix; Int. Caps., internal capsule; Lat. V., body of lateral ventricle; 3 V., third ventricle. (Testut.) similar occurrences. Some mental associations are developed, with activity over large areas of the cortex before the conscious orders go out from definite areas to the muscles. These orders being for certain contractions to occur that shall produce certain movements. In the corpus callosum are various small masses of gray matter, some of which are called "nuclei," "ganglia," "commissures," etc. On the floor of the ventricles, and the upper part of the medulla other small gray masses are found. Many of the cranial nerves originate in this area. 226 THE NERVOUS SYSTEM The Cerebellum.-The cerebellum, or hind-brain is in the posterior fossa of the cranium covered by the tentorium. Its gray matter is on the outside, projecting inward in tooth-like or dentate processes. Its main portion consists of three parts, a middle and two lateral divisions called hemispheres. The median portion, also called the vermix is very small, so it can be hardly seen. (Fig. 206.) The upper surface of the cerebellum is nearly flat (Fig. 207.) and the lower surface convex (Fig. 208). Fissures on both surfaces run transversely, dividing the sub- stance into layers, leaves or laminae. Fig. 206.-Median section through the third and fourth ventricles. Left half. M.C., middle commissure. (Testut.) They are similar to the gyri of the cerebrum in having white fibers in a mass below, covered with gray matter. The cerebellum is connected with the other parts of the brain by three pairs of bands. One pair goes to the oblongata, one to the pons and the other pair to the mid-brain or isthmus. (The isthmus is a narrow neck by which the cerebellum is connected with the structures below.) The Pons Varolii or Bridge of Varolius.-This structure is mainly composed of fibers which run in various directions. One set goes through the central part connecting the isthmus to the medulla. Another set passes horizontally, connecting the. two lateral hemis- pheres of the cerebellum. GENERAL CONSIDERATIONS OF THE BRAIN 227 In the midst of these wdiite fibers are several collections of cells, among which are the nuclei or places of origin of the fifth, sixth, seventh and eighth cranial nerves. Fig. 207.-Upper surface of cerebellum. The lingula and cacumen are concealed by overhanging parts. The label "monticulus" is on the culmen. (Testut.) The Oblongata.-This is also known as the medulla oblongata or spinal bulb, and may be considered as a connecting link between the Fig. 208.-Under surface of cerebellum. The hemispheres are pulled apart to give a view of the inferior vermis. The nodule is between the uvula and the fourth ventricle. (Testut.) other parts of the brain and the spinal cord. In its structure it presents similarities to both. 228 THE NERVOUS SYSTEM As the other parts of the brain have been considered, it will be well to turn ahead to the section describing the spinal cord so as to note the relations of the oblongata to both. In comparing the medulla with the cord it should be noted that while in the brain the gray matter is mostly on the outside, in the cord it is in the center, shaped crudely like a letter "H." The white substance is separated by the legs of the "H" into three columns on each side, ventral, dorsal and lateral. These divisions, both the gray and the white are continued upward from the cord into the medulla, but their relations are changed. Fig. 209.-The pons and oblongata, ventral view. (Testut.) The gray matter is broken up into a number of separate parts, and there are a number of additional nuclei. The white fibers, some of which carry messages to the brain, some from it, seem to be continued upward into the corresponding part of the medulla, but this is not always the case, and the bundles of fibers may be turned in new directions in a very complicated fashion. The oblongata rests upon the basilar process of the occipital bone, is about 11 inches long, extending from the lower margin of the pons to the beginning of the spinal cord just below the " decus- sation of the pyramids." It is larger above, tapering below to about the same size as the upper region of the cord. (Fig. 209.) The Decussation of the Pyramids.-On the ventral surface of the medulla is a longitudinal fissure, the ventro-median fissure, which GENERAL CONSIDERATIONS OF THE BRAIN 229 is interrupted by a criss-cross of nerve bundles. On each side of the fissure is a white body which seems to be directly continuous with the ventral column of the cord. These are the ventral (anterior) pyramids, and their crossing over the fissure at their lower part, so Fig. 210.-Transverse section of the oblongata at its lower end. (Testut.) the fibers on the right go to the left side, is called the " decussation of the pyramids." This is the arrangement by which the left side of the brain controls the right side of the body, and vice versa. (Figs. 210, 211.) Fig. 211.-Transverse section of oblongata at the decussation of the pyramids. (Testut, after Duval.) From the medulla, come the cranial nerves from the sixth to the twelfth, inclusive, and the first spinal nerve. Functions of the Cerebrum.-For many centuries it has been recog- nized that the cerebrum is the seat of conscious sensation and intel- ligence. It has been known that the development of the brain was connected with and dependent upon the development of the cortical area of the cerebrum. 230 THE NERVOUS SYSTEM If, for any reason the sutures of the skull in an infant are united before the brain has had time to develop, the mentality of the child will be stunted to a greater or less degree. Injuries to certain areas of the cortex have resulted in loss of memory. These facts and certain experiments show that if the cortex is removed all the sensation, intelligence and thought that characterize the highest psychical life of man is destroyed. Abnor- malities of the cortical structure may be the cause of the perverted reasoning of the insane and the characteristics of the degenerate. The cortex of the cerebrum contains a variety of nerve cells, arranged in some five layers. Some of these cells are supposed to have only the work of connecting one part of the cortex with another part. Some are shaped like a pyramid and are called "pyramidal" cells. Many of these send their axones to the medulla. Reflexes.-Messages are carried to the brain by "afferent" nerves, while the "efferent" nerves carry a message from the brain to the periphery. Both are concerned in most actions, as the mes- sages coming from the outside to the brain provoke some response, that is, some reflex. As an instance, a bright light thrown into the eye causes the reflex of contraction of the pupil. A touch on the eyeball, causes the reflex of winking. The smell of appetizing food starts the secre- tion of saliva. Such reflexes are impossible to control or prevent, and are spoken of as unconditional reflexes. Another kind of reflex, called conditioned reflexes may be obtained under certain conditions or may be brought out by training or education. They are subject to various forms of inhibition both internal and external. The method of obtaining them is as follows. If a certain sensory stimulation is given, as a note of a definite number of vibrations per second, there is no effect upon the secre- tion of saliva, but, if the salivary glands are stimulated by acid at the same time, after a while the reflex of salivary flow comes from the note alone without the acid. Many reflexes occur through the mediation of the cerebral cortex, and many others through the spinal cord. Those of the spinal cord however, may be inhibited by the brain. The involuntary jump that occurs upon hearing a sudden loud noise may be inhibited by the higher centers in the brain, so that in time, the individual makes few involuntary movements, or noticeable reflex actions. Motor Areas of the Brain.-A function of the cortex of very great interest is that connected with motor activity. By experimental work it has been established that the centers for outgoing messages that activate the skeletal muscles are grouped around the central or Rolandic fissure. If the form of a miniature human body is inverted and laid along the Rolandic fissure, it will indicate the order in which the various motor areas occur. The lowest part controls the head and face, GENERAL CONSIDERATIONS OF THE SPINAL CORD 231 while the areas progress toward the toes at the upper part. In other words, the areas follow' the order in which the cranial and spinal nerves emerge from the brain and cord. The pyramidal cells of the motor areas of the cortex give rise to the out-going messages w'hich proceed along their axones to the motor nuclei of the cranial or spinal nerves. From the cells of these nuclei, other axones carry the messages to the muscles or other parts that are to be stimulated. There may be intermediate stations w'here the impulse is accentuated or augmented, as the axones pass through the cerebellum or medulla, but there must always be these two stations. Some axones from the brain, cross from one side to the other at the "decussation of the pyramids," going down to the spinal neuron on the opposite side to that in w'hich the impulse originated. Center for Speech.-Nearly all the brain functions are bilateral, but the area for speech w'hich is located in Broca's convolution in the posterior part of the frontal lobe, has been thought to exist on the left side only. Persons with right sided paralysis, due to lesions on the left side of the brain are generally unable to speak, but if the paralysis is on the left side, showing involvement of the right side of the brain, the power of speech is generally present. More or less successful efforts have been made to restore speech to those par- alyzed on the right side by training the left hand to skill, with the idea that there is an undeveloped speech center on the right side of the brain which may be made to function by education of the con- tiguous motor areas. Functions of the Cerebellum.-It is supposed that the cerebellum coordinates muscular movements-especially those concerned in equilibrium and locomotion. It may be an augmenting apparatus for voluntary movements. There is a lack of agreement among physiologists in regard to the w'ork done by the cerebellum. Its loss seems to affect the muscular sense and those of position and direction. Each half is connected with the corresponding half of the body. Functions of the Medulla.-Here are centers that control the activ- ity of the respiratory and circulatory systems. The movements of the organs concerned are rhythmic and automatic, but not volun- tary. By means of the vagus, whose nucleus of origin is in the medulla, the heart may be reflexly controlled through the cardio- inhibitory centers. The secretion and motions of the alimentary tract may also be reflexly affected through the same nerve. GENERAL CONSIDERATION OF THE SPINAL CORD WITH MOTOR AND SENSORY PATHS. The spinal cord or myelon is the second part of the cerebrospinal axis and is the direct continuation of the medulla. It extends from the foramen magnum, or from the "decussation of the pyra- mids" to the lower border of the first lumbar vertebra. It is about 18 inches long, on the average, and varies in dia- meter from f to 1 inch. It terminates in a slender filament, called the "filum terminale" (Fig. 212). The cord does not occupy the full length of the spinal canal, but from the lumbar enlargement the sacral and coccygeal nerves come off and hang down into the lower part of the canal in a formation to which is given the name, "cauda equina" or horse's tail from its resemblance to that object. The cord has coverings similar to those of the brain, with corresponding uses. The dura is on the outside, extending to the intervertebral foramina; the pia, a delicate mesh of bloodvessels close to the cord, and the arachnoid between the two, producing the arachnoid fluid. This fluid serves as a water-bed or cushion to protect the cord from external vio- lence. From the cord on each side are given off spinal nerves to supply the skeletal muscles of the body below the head, and transmit the sensory impressions from the same regions. A cross-section of the cord (Fig. 213), shows it to be composed of gray and white substance. The gray is placed in the center, the white, outside. On the surface are a number of creases. In the middle line of the front is a deep and rather broad fissure, called the ventral or ventro-median fissure. In the middle line posteriorly is a less well marked cleft, the dorsal or dorso-median fissure. At each side of the dorsal fissure, about one-fourth of the distance toward the front is the slight dorso-lateral fissure, and between this and the dorsal is the dorso-intermediate fissure. The nerves given off from the cord arise by two Fig. 212.-Spinal cord, oblongata and pons. Left-hand figure is ventral view, right-hand is dorsal. (Testut.) GENERAL CONSIDERATIONS OF THE SPINAL CORD 233 roots, the dorsal root which comes from the posterior horn of the gray matter, at the dorso-lateral fissure, and the ventral, coming from the ventral horn some distance to the outer side of the ventral fissure. The White Matter of the Cord.-Between the ventral fissure and the ventral roots the white fibers form the anterior or ventral column. Between the ventral and dorsal roots is the lateral column, while between the dorsal roots and the dorsal fissure is the dorsal or pos- terior column, which is subdivided by the dorso-intermediate fissure into the dorso-lateral and the dorso-median columns. (Fig. 214.) Fig. 213.-Transverse section of the spinal cord at the middle of the thoracic region. The neuroglia septum has been removed from between the dorsal columns. (Testut, after Pierret.) The Gray Matter of the Cord.-The gray matter of the cord is arranged in the shape of a very crude letter " H," having the front horn or cornu much wider than that at the rear. From the pos- terior part of the ventral cornu the lateral cornu juts out, more pronounced in the upper dorsal region. The cross-bar or gray commissure has an aperture which indicates a small canal, continu- ous throughout the cord, which is called the "central canal of the cord." It communicates with the fourth ventricle of the brain. By reference to Fig. 215 it will be seen that the size of the cord and the proportion of gray matter varies at different levels. The 234 THE NERVOUS SYSTEM cervical enlargement and the lumbar enlargement mark the giving off of spinal nerves to the upper and lower extremities respectively. Anterior Roots.-The large anterior horns of the cord contain large cells whose axones pass out of the spinal canal as the motor portion of the spinal nerves. All spinal nerves are mixed, that is, they contain efferent or motor fibers and afferent or sensory fibers running side by side. Fig. 214.-Diagrammatic ideal transverse section of the spinal cord. On the left side are shown the gross divisions; on the right side, the conduction paths. (Gerrish.) Posterior Roots.-The sensory fibers are derived from the posterior cornu of the gray matter. Unmedullated fibers pass from one side to the other of the gray matter, forming the gray commissure. White Fibers of the Cord.-The white substance of the cord is formed by medullated fibers either going down the cord from the GENERAL CONSIDERATIONS OF THE SPINAL CORD 235 brain or upward to the brain. They form distinct tracts that have been pretty thoroughly traced and their functions determined. A white commissure, placed in front of the anterior part of the gray commissure, connects the two sides of the white matter in the cord. The cord is also divided into seg- ments corresponding to the number of the vertebrae. Functions of the Spinal Cord.-Con- duction.-As will be inferred from the above, the conduction of messages is the function of many of the fibers in the cord. The columns of white matter seen in the cord do not show much difference anatomically but physiologically there is a great differ- ence. By referring to Fig. 214 the limits of the columns may be noted. The direct or anterior pyramidal tract and the crossed pyramidal tract convey motor impulses. The cross pyramidal tracts come directly from the pyramidal cells in the oblongata, and cross from one side to the other at the "decussation of the pyramids." Motor impulses from the motor areas of the brain pass down these tracts to the motor cells in the anterior cornu of gray matter in the cord, thence going by spinal nerves to their peripheral terminations. Sensory impulses from the periphery pass into the cord, then may go through several columns to the brain. The fibers in these tracts seem to cross from one side to the other in any part, so that section of half the cord produces anesthesia of the opposite side of the body below the cut. Association.-Apparently, the work of some tracts is that of association. That is, fibers go from one side of the cord to the other; they go up and down in the cord for a short dis- tance. They may be ascending or descending, carrying sensory or motor impulses. They form a mechanism by which the different segments of the cord are brought into association. Fig. 215.-Transverse sections of the spinal cord at different levels. (Testut, after Erb.) 236 THE NERVOUS SYSTEM The fibers in the posterior tract, known as Burdach's column seem to assist in regulating and coordinating voluntary movements. The sense of pressure and of muscular sense are probably located in this column, which has direct connection with the cerebellum. Transference.-Another function of the cord is the transferring of impressions from one place to another, as, in the case of pain in the knee-joint when the trouble is really located in the hip-joint. Reflex Action.- This is one of the very important functions of the cord, and takes place without the mediation of the brain, though as seen above, reflexes occur with the centers in the brain, as well. For a reflex act to occur, the so-called "reflex arc" must be intact. Reflex Arc.-A reflex arc consists of a receiving neuron to which some stimulus comes via the sensory fibers in a cranial or spinal nerve; the association of the branches of this neuron with the branches of a motor neuron, from which a message goes out through a cranial or spinal nerve to the periphery. If all the parts of this arc are intact, a reflex can occur, but if any part is impaired, the reflex is lacking. Not only may this reflex affect a voluntary muscle, but it may also influence the vasomotor and other nerves of the sympathetic system. The number of reflex actions that occur through the spinal cord is very large. Certain tracts in the cord seem to be devoted to these actions. Augmentation.-The strengthening of impulses that enter the cord occurs by the prolongation, upward and downward of the sensory impulses, so that communication with several groups of motor cells occurs. The association function of the cord is united with this. Coordination and Automatic Action.-Certain voluntary actions, such as walking, writing, etc., by many repetitions become so entirely familiar, the cord attends to their performance without the mediation of the brain. Special Centers.-Through the reflexes, certain centers in the cord regulate many acts, as defecation, micturition, etc. Through stimulation of various parts of the spinal cord and the mediation of the rami communicantes, the involuntary muscles of various organs as the heart, stomach, intestines and bloodvessels may be made to contract or relax. THE CEREBROSPINAL NERVES AND PLEXI. Having considered the cranial and spinal centers, it remains to discuss the branches of each which carry the messages to and fro. Those from the brain are the cranial nerves, and those from the cord are spinal nerves. All the spinal and some of the cranial nerves are mixed nerves, that is, they contain both motor and sensory fibers. THE NAMES AND DISTRIBUTION OF CRANIAL NERVES 237 The spinal nerves arise by two roots from the cord. The anterior or ventral root is motor, several bundles of axones coming from the motor cells in the anterior horns of gray matter. The posterior or dorsal root is sensory, with a ganglion on it. It comes from the posterior horn of the cord. The ganglion on the root contains the cells, from which two processes arise, one going back to the cord, the other out to help form the spinal nerve. The two roots unite into one trunk that passes out through the inter- vertebral foramen. (Fig. 216.) Fig. 216.-Plan of the constitution of a spinal nerve. (Keiller.) Just after leaving the spinal canal, a recurrent branch is sent back. It receives a branch from the sympathetic and goes into the spinal canal to supply the meninges and bloodvessels. The spinal nerves divide into anterior and posterior primary divisions, the posterior division later dividing into internal and external branches. The anterior division sends a branch, the ramus communicantes, to connect with the neighboring ganglia of the sympathetic. THE NAMES AND DISTRIBUTION OF THE CRANIAL NERVES. From the under surface of the brain, 12 pairs of nerves emerge to be distributed to the following structures. They are indicated by number as well as having definite names (Fig. 209). Of the 12, the first and second contain only afferent fibers; third, fourth and sixth have efferent fibers only; the fifth, ninth and tenth have both afferent and efferent fibers; the seventh, eleventh and twelfth only efferent, and the eighth only afferent fibers. First pair. Olfactory, or nerve of smell is distributed to the upper part of the nasal cavity. Second pair. Optic, or nerve of sight, is distributed as the retina to the eyeball. Third pair. Oculomotor, is distributed to the eyeball muscles, with the exception of the external rectus and the superior oblique. Fourth pair. Trochlear, goes to the superior oblique muscle of the eyeball, with motor impulses. 238 THE NERVOUS SYSTEM Fifth pair. Trifacial, supplying the front of the scalp, the exter- nal ear, the cheek, teeth, gums and front of tongue with sensation, and the muscles of mastication with motor impulses. Sixth pair. Abducent, a motor nerve to the external rectus of the eyeball. Seventh pair. Facial, supplying motor impulses to the super- ficial muscles of the face and some of those of the throat. Eighth pair. Auditory, the nerve of hearing and equilibrium, distributed to the labyrinth of the internal ear. Ninth pair. Glossopharyngeal, the nerve of taste, distributed to the tongue, with fibers of ordinary sensation and some motor fibers to the tongue and pharynx. Tenth pair. Vagus or Pneumogastric, distributing sensory fibers to the external ear; motor and sensory to the pharynx, larynx, trachea, lungs, esophagus, stomach and heart, with some to the liver. Eleventh pair. Spinal Accessory, sending motor fibers to the trapezius and sterno-mastoid muscles. Twelfth pair. Hypoglossal, the motor nerve of the tongue. THE SPINAL NERVES. There are 31 pairs of spinal nerves, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal. The first cervical nerve comes from the medulla, and passes out of the canal above the atlas. The eighth cervical passes between the seventh cervical and the first thoracic vertebrae. The first 7 cervical nerves are named from the vertebra below them, while the thoracic, lumbar and sacral nerves are named from the vertebra above them. The dorsal primary divisions of the spinal nerves supply the skin on the back of the head, neck, trunk and gluteal regions, and the muscles that act directly upon the spinal column. These dorsal (primary division) nerves divide into internal and external branches, but they are smaller than those that form the ventral division. The nerves of the ventral primary division are joined by rami com- municantes from the neighboring sympathetic ganglia, by which the structures supplied by the sympathetics may be reflexly affected thiough stimulation of the spinal nerves (Fig. 217). In the thoracic region, the ventral division supplies the inter- costal muscles, as the intercostal nerves. Elsewhere, they form plexi, from which the nerves to the peri- phery start. (Fig. 218.) There are four plexi, the cervical, the brachial, the lumbar, and the sacral. The Cervical Plexus.-This is an intricate combination from the first four cervical nerves. The parts supplied are the muscles about the head and neck, the trapezius, levator scapulae, scalenus medius, Fig. 217.-Topography and distribution of the spinal nerve roots. (Gerrish.) 240 THE NERVOUS SYSTEM 0 > Z 0 r Fig. 218.-Anterior surface of the spinal cord, showing the spinal nerves and their connections with the sympathetic trunk on one side. (Testut.) THE SPINAL NERVES 241 and the sterno-mastoid. One long nerve, the phrenic, supplies the diaphragm. The nerve on the right side supplying the under surface while that on the left supplies the upper surface of the muscle. (Fig. 219.) Fig. 219.-Plan of cervical plexus. (Gerrish.) The Brachial Plexus.-This is formed from the fifth, sixth, seventh and eighth cervical, and the first thoracic nerves, with branches from the fourth cervical and the second thoracic. These nerves, by their union before breaking up into terminal branches, provide 242 THE NERVOUS SYSTEM fibers from most of the five segments for each terminal branch. This association is important in bringing about the orderly move- ments of the muscles of the upper extremity. Reference to the diagram (Fig. 220), will show the fifth and sixth cervical nerves uniting to form the upper trunk; the seventh cervical forming the middle trunk, and the eighth cervical and first thoracic forming the lower trunk. Each trunk then divides into anterior and posterior branches. The anterior branches of the upper and middle trunks form the outer cord. The anterior division of the lower trunk forms the inner cord, while the posterior divisions of all three trunks form the posterior cord. (Fig. 221.) Fig. 220.-Diagram to show the component spinal nerves in the peripheral branches of the brachial plexus. The outer cord divides into the musculocutaneous and the outer head of the median; the inner cord into the inner head of the median, the ulnar, the internal cutaneous and the lesser internal cutaneous; the posterior cord into the circumflex and the musculospiral. Other nerves are given off to the rhomboidii and the subclavian muscles. The suprascapular nerve to the supraspinatus and the infraspinatus; the posterior thoracic nerve to the serratus magnus; the external and internal anterior thoracic nerve to the pectoralis major and minor muscles; and the long subscapular nerve to the latissimus dorsi muscles. The muscidocutaneous nerve supplies the coracobrachialis, the biceps and the brachialis muscles. The median nerve passes down on the inner side of the arm between the biceps and triceps muscle, and then passes down the middle of the front of the forearm, supplying all the muscles on the front of the THE SPINAL NERVES 243 forearm (except the flexor carpi ulnaris and a part of the flexor pro- fundus digitorum), and the short muscles of the thumb that are on the radial side of the flexor longus pollicis. A deep branch of the median is the anterior interosseous. Branches are sent to the skin over the muscles supplied and to the joints those muscles move. The ulnar nerve passes down the inner side of the arm, then between the internal condyle and the olecranon process, and into the forearm. It supplies the flexor carpi ulnaris and the half of the flexor profundus digitorum muscles. Fig. 221.-Plan of brachial plexus. (Gerrish.) The circumflex nerve supplies the deltoideus muscle and the shoulder-joint. The musculospiral nerve descends diagonally across the back of the arm, and at the elbow divides into the radial and posterior inter- osseous. This nerve, with the two terminal branches supplies all the extensor muscles of the arm, forearm and hand. The distribu- tion of the nerves of this plexus to the skin is observed in (Figs. 222 and 223). The Lumbar Plexus.-This is formed from the first, second and third lumbar nerves, with a part of the twelfth thoracic and the fourth lumbar. It is embedded in the psoas magnus muscle. (Fig. 224.) 244 THE NERVOUS SYSTEM Fig. 222.-Cutaneous nerves of the upper limb, ventral aspect. (Keiller.) THE SPINAL NERVES 245 Fig. 223.-Cutaneous nerves of the upper limb, dorsal aspect. (Keiller.) 246 THE NERVOUS SYSTEM Fig. 224.-Plan of lumbar plexus. (Keiller.) Fig. 225.-Plan of sacral plexus. (Gerrish.) THE SPINAL NERVES 247 Fig. 226.-Deep nerves of buttocks and back of thigh. (Testut.) 248 THE NERVOUS SYSTEM Branches from the plexus supply the muscles on the front and inner side of the thigh, the abdominal wall and the reproductive organs. Fig. 227.-Deep nerves of the back of the leg. (Testut.) Among the principal branches are the iliohypogastric and the ilioinguinal which go to the abdominal wall muscles. The anterior crural nerve supplies the iliacus, the pectineus, the rectus femoris and the vasti muscles. THE SPINAL NERVES 249 The obturator nerve supplies the adductor muscles, obturator internus and externus and the sartorius, besides the hip-joint. It may be taken for granted that a nerve that supplies a muscle also sends a branch to the joint that muscle moves and to the skin over both. (Hilton.) The Sacral Plexus.-This is formed by the part of the fourth lumbar, the fifth lumbar and the first four sacral with branches from the fifth sacral and the coccygeal. (Fig. 225.) Fig. 228.-Plantar nerves. (Testut.) The branches of this plexus divide into anterior and posterior divisions. The posterior set arises from the back of the plexus and supply the extensor aspect of the lower extremity. (They are shaded in the diagram.) The anterior set arises from the front of the plexus and supplies the flexor muscles of the lower extremity. 250 THE NERVOUS SYSTEM Fig. 229.-Deep nerves of the front of the leg. (Testut.) 251 THE SPINAL NERVES The most noticeable branch of this plexus is the great sciatic, a large trunk that passes out of the pelvis to the back of the thigh. Branches are given off to the semitendinosus, the semimembranosus, adductor magnus and biceps femoris muscles. The nerve runs deep in the muscles of the thigh and above the knee divides into the internal and external popliteal nerves. (Fig. 226.) Fig. 230.-Nerves of the dorsum of the foot. (Testut.) The internal popliteal passes down as far as the lower border of the popliteus muscle where it becomes the posterior tibial. From this, muscular, articular and cutaneous branches are given off. The posterior tibial divides into the internal and external plantar nerves at the ankle. (Figs. 227 and 228.) The external popliteal passes down on the outer side of the knee and divides into the musculociitaneous and the anterior tibial. Figs 229 and 230.) 252 THE NERVOUS SYSTEM By a study of these illustrations it will be seen that the sciatic nerve supplies the flexor muscles of the thigh and all the muscles of the leg with the skin and joints thereof. THE SYMPATHETIC NERVOUS SYSTEM. Location and Arrangement.-The sympathetic or autonomic nervous system has to do with the control of the so-called vegetative processes of the body. All the involuntary or smooth muscle fibers in the walls of bloodvessels and of the hollow viscera in the body, are governed by the sympathetic. All the epithelial cells in glands or viscera have fibers from this system to control their activity. The system consists of the prevertebral ganglia, plexi and sporadic ganglia in various places. Prevertebral Ganglia.-On each side and in front of the spinal column are reddish-gray masses of nerve tissue., extending from the base of the brain to the coccyx. While there are 31 pairs of spinal nerves, the number of sympathetic ganglia do not correspond, as their number is from 20 to 23. Three pairs of ganglia, the superior, middle and inferior cervical are in the neck; 10 or 11 are in the thoracic region; and the rest are in the lumbar and sacral region, with a single ganglion in front of the coccyx (ganglion impar.). The ganglia are connected by the gangliated cord which extends from the superior cervical to the ganglion impar, making an appear- ance like a chain of beads with a pendant. These prevertebral ganglia are connected with the cerebrospinal nerves by medullated fibers from the latter and non-medullated fibers from the sympathetic. These are the rami communicantes, gray and white, according to the absence or presence of the medul- lary material. The superior cervical ganglion is connected with the four upper cervical nerves which form the cervical plexus, and with several cranial nerves, including the vagus. It sends filaments to the upper cardiac nerve. (Note its relation to the suboccipital muscles.) The middle cervical ganglion connects with the fifth and sixth spinal nerves, and with the superior and inferior ganglia. It sends branches to the thyroid gland and to the upper cardiac nerve. The inferior cervical ganglion connects with the middle ganglion, the seventh and eighth cervical and first thoracic spinal nerves. It sends branches to the cardiac nerve. Physiologically, the cervical sympathetics are very important, and a careful study of their relations to surrounding and distant structures is necessary for those engaged in physio-therapeutic work. It is particularly desirable to study the effects produced through them by excessive muscular tension of the back of the THE SYMPATHETIC NERVOUS SYSTEM 253 neck. The limits of this work will not permit any detailed discus- sion of these relations. The Sympathetic Plexi.-Of the thoracic ganglia the upper ones take part in the formation of a plexus about the aorta, while the lower ones (splanchnic or visceral nerves), help in the formation of the solar plexus. From the lumbar ganglia branches help form the diaphragmatic or phrenic plexus, the suprarenal, the renal, and the coeliac j51exi. In the sacral ganglia connection is made with the sacral nerves forming the pelvic plexus. From this the pelvic viscera are supplied with motor, vasomotor and secretory fibers. The solar plexus is a great mass of nerve cells and fibers, both cerebrospinal and sympathetic that sends fibers to the abdominal organs and abdominal wall muscles, controlling motor, vasomotor and secretory activity. It is sometimes called the "abdominal brain." Sporadic Ganglia.-Besides the above collections of gray cells and fibers, each organ has one or more groups of cells within its substance, influencing its action and its blood supply, automatically, and with a definite rhythm peculiar to each organ. Relation of Cerebrospinal and Sympathetic Systems. - Vasomotor System.-It has been seen that the two systems are connected by the gray and white rami communicantes. From this union, the one system influences the other. Their common meeting place is in the walls of the bloodvessels. Here are the vasomotor nerves, consisting of two sets of fibers, the vasoconstrictor and the vasodilator. The vasomotor nerves carry the messages to the walls of the blood- vessels to either contract the involuntary tissue and make the caliber smaller, or to relax, and increase the caliber. Fear, anger and other emotions, mediated in the brain have definite effects upon the various organs. Fear blanches the skin, weakens the muscles, especially the extensors, and changes the rhythm of the heart. It may stop digestion midway. Fear is a mental emotion, located in the sensorium, but working out through the blood supply of these various parts. Relation of the Sympathetic System to the Functions of the Body.- Under normal conditions it is supposed the sympathetic or auto- nomic nerves are always excited reflexly and involuntarily. Sen- sory impressions that initiate the reflexes are visual, auditory, olfactory, gustatory, pressure, temperature, pain, hunger, thirst, etc. The response that completes the reflex may be excitatory or inhibitive. The excitatory response may be either motor or secre- tory. The motor responses may be in the sphere of the vasomotor, cardiomotor, visceramotor or pilomotor phenomena. The secretory response may be the production of the salivary secretion, gastric juice, pancreatic juice, bile, urine, sweat, etc. Or the response may be to inhibit motor or secretory activity. 254 THE NERVOUS SYSTEM The Subconscious Mind.-The study of psychology and physiology meet in the consideration of the subconscious mind. What the conscious mind is to the cerebrospinal nervous life, the subconscious is to the sympathetic realm, or vegetative life. There is a wide- spread belief that the conscious mind can influence if not control the subconscious mind by means of suggestion; either from one's self or through another. The explanation of the wonderful appar- ent results of the "Cone" methods depends upon the fact that the control of the vital processes of life, respiration, circulation, diges- tion, assimilation, etc., are through the subconscious mind and its sympathetic servant. THE NERVES OF SPECIAL SENSE, WITH THEIR SENSE ORGANS. The Optic Nerve and the Eye.-The eyeball and its appendages are placed in the orbital fossa, in a bed of fat and areolar tissue. It is not perfectly spherical, having a slight increase of the curvature at the cornea, in front, and a slight flattening behind. The enucleated eye shows on the outside of the ball a fibrous covering, which is very dense and white, the sclerotic. In the front of this is a clear transparent structure like the crystal of a watch, called the cornea. Inside the fibrous structure is a vascular coat with much dark pigment, the choroid. Applied to the back of the sphere, is the spread-out nerve of sight, the retina. Filling the sphere, and keeping it from wrinkling and so inter- fering with sight, is a transparent, jelly-like mass, the vitreous. This keeps the eyeball plumped out, yet elastically firm. Back of the cornea is the crystalline lens, a bi-convex structure that is perfectly transparent. (Fig. 231.) Between the cornea and the lens hangs a curtain with a hole in it, which corresponds in use and appearance with the diaphragm of a camera. The curtain is the iris, varying in color with different individuals, and the hole is the pupil, which becomes larger or smaller according to the amount of light thrown into it. The space between the cornea and the iris is the anterior chamber of the eye, which with the posterior chamber contains the aqueous humor, or a watery material which is refractive. The space back of the iris is the posterior chamber. The normal stimulus of the retina is light, and this is admitted through the pupil, refracted by the cornea, lens, aqueous and vitre- ous humors. Light coming from an object is refracted so its image falls on the retina in an inverted position, but through experience we have learned to imagine things in their proper position, in spite of the upside-downness of them. THE NERVES OF SPECIAL SENSE 255 Attached to the eyeball are six muscles which turn it in various directions, increasing or decreasing the convexity of the front and shortening or lengthening the eyeball. The eyelids cover the ball, and attached to their edges are the cilia or lashes. Lining the lids and covering the exposed surface of the eyeball is a mucous membrane, the conjunctiva. Fig. 231.-The right eye in horizontal section, showing the upper surface of the lower segment. Diagrammatic. (Testut.) At the inner border is the opening of a tube, that leads into the nasal cavity and carries the tears and any small particles from the surface down into the nose. This is the lachrymal duct and the little gland that secretes the tears is the lachrymal gland. The eyes are closed by the contraction of the orbicularis palpebrarum, a muscle that surrounds the eye. The Auditory Nerve and the Ear.-The organ of hearing is divided into three parts, the external, middle and internal ear. 256 THE NERVOUS SYSTEM The External Ear.-The external ear is a flaring cartilaginous structure, which collects the sound waves and focuses them into the external auditory meatus, a tube leading to the partition between the external and middle ear. This tube is the epithelial lined audi- tory canal in the temporal bone, and contains some cells which secrete cerumen or wax. This wax catches dust and any small insects that attempt to get into the ear. (Fig. 232.) Fig. 232.-Vertical section through the external auditory meatus and tympanum passing in front of the fenestra ovalis. (Testut.) At the inner end of the meatus is a membrane that separates the external and middle ear. It is the membrana tympanum. The Middle Ear.-Back of this membrane is a space, the tym- panum, which contains three small bones or ossicles, the malleus, incus and stapes. These are arranged in a series, so the malleus is in contact with the membrana tympanum, and is moved by its vibration; the incus joins the malleus and the stapes. The last, connects the others to the opening between the middle and internal ear, the fenestra oralis. Sound waves throw the membrana tympanum into vibrations, which the chain of bones transmit to the fenestra ovalis. Opening into the tympanic cavity is a tube, about 1| inches long, which extends to the back of the pharynx. This is the Eus- THE NERVES OF SPECIAL SENSE 257 tachian tube, carrying air from the mouth or nose to the middle ear, so as to equalize the pressure within and without the ear, on each side of the membrana tympanum. The Internal internal ear begins back of the fenestra ovalis, and consists of a labyrinthine sac, lined with a very sensitive membrane, and filled with a fluid in which are some hard particles. This sac is in several parts, the most anterior of which is the saccule. From it extends a long coiled process, the cochlea. The posterior sac is the utricle, from which three semicircular canals emerge, going in three different directions. The function of these has to do with maintaining equilibrium. The auditory nerve is distributed upon an area of the utricle, and stimuli reach it by the waves of sound transmitted through the membrana tympanum, the chain of bones, and the fluid in the sac, finally reaching the auditory center in the brain as sound. Neuro-epithelial cells with waving cilia are concerned in the final step. The Gustatory Nerve and the Tongue.-The tongue is the principal organ of taste and of articulate speech, helping in mastication and deglutition. It is highly sensitive to touch, heat and cold. It is an index of the body health, showing the degree of elimina- tion that is going on. It is occasionally a means of diagnosis, as its appearance is sometimes characteristic of special conditions. The tongue consists of a muscle, the lingualis, which has a median raphe, and is attached to the hyoid bone. Associated with it are several others, the genioglossus, the hyoglossus, the styloglossus and the chondroglossus muscles. A large variety of movements are possible to this combination. The tongue is covered with a mucous membrane, the back part of which contains the "taste buds," or terminals of the gustatory nerve. (Fig. 233.) The Olfactory Nerve and the Nose.-The nose is a prominent part of the face, and is formed mostly by cartilage. The two nasal bones at the upper part, the vomer and the ethmoid forming the septum, serve to support the cartilage. The openings visible in front are the anterior nares, while those posteriorly which communicate with the pharynx are the posterior nares. The nasal fossa contains three bodies, the superior, middle and inferior turbinated. The superior body is osseous, but the other two are cartilaginous. These bodies are scroll-shaped, providing a large extent of surface for mucous membrane. (Figs. 234, 235.) Lining the nose, the septum, the turbinated bodies and communi- cating with the similar lining of the naso-pharynx, the ethmoid cells, etc., is a mucous membrane, rich in bloodvessels. This is the 258 THE NERVOUS SYSTEM Schneiderian membrane. On that area covering the superior tur- binated bodies the olfactory nerve is distributed. The nose is also a special external organ of respiration, and the intricate convolutions of the interior are to provide a large vascular surface by which the incoming air may be warmed before going into the lungs. Fig. 233.-Dorsal surface of the tongue. (Testut.) Nerves of Touch and General Sensation.-The special organ of the sense of touch is the skin. As the skin will be described in detail in connection with the organs of elimination, no description of it will be given here. The muscles, tendons and joints are supplied with sensory nerves from which is developed what is sometimes called the "muscular 259 THE NERVES OF SPECIAL SENSE Fig. 234.-Coronal section of nasal fossae at the plane of the second molar tooth seen from behind. (Hirschfeld.) Fig. 235.-Sagittal section of face and neck, showing external wall of right nasal fossa. (Testut.) 260 THE NERVOUS SYSTEM sense" or the kinesthetic sense, by which we are conscious of the position in space occupied by our members and the movements performed by them, etc. QUESTIONS. Name the coverings of the brain and spinal cord. Of what use is the cerebrospinal fluid? Name the divisions of the brain. Compare the functions of the cerebrum and cerebellum. What is meant by "motor areas" of the cortex? What are afferent nerves? What is a "reflex"? Describe "unconditional reflexes." What structures are necessary to a reflex action? In what part of the brain is the "respiratory center"? Describe the gray matter of the spinal cord. How is a spinal nerve formed? In what direction do motor influences pass in the spinal cord and nerves? What is meant by "column" in the white matter of the cord? Name the functions of the spinal cord. Which of the cranial nerves have to do with the digestion of food? What is a "ramus communicantes"? What general region receives its motor supply from the brachial plexus? From what plexus does the innervation of the diaphragm come? What is the principal nerve coming from the sacral plexus, and what muscles receive motor impulses from it? What is the "autonomic" nervous system? What is the "solar plexus"? How are the cerebrospinal and autonomic systems related? Describe "vasomotor" nerves and their functions. Name the "sense organs." What is "kinesthetic sense"? CHAPTER VIII. THE CIRCULATORY SYSTEM. The blood in the body is contained in a system of closed tubes, into which two other tubes open. This makes for a continuous flow of blood from one part of the body to another, with varying amounts in the different regions at different times. The life of every part of the body is dependent upon an adequate supply of blood. There must be some way to insure the flow of blood as whatever amount there is in the tubes must answer for all needs. The organs concerned are the heart, arteries, veins, capillaries and lymphatics. Two pumps, one of them a force pump, the other a suction pump provide the power to keep the blood in motion. The force pump is the heart. The suction pump consists of several mechanisms, not located in any one spot. THE ANATOMY OF THE HEART. The heart is a hollow muscular organ, forming the central reservoir for the blood, and a pump. It consists of four chambers, two on each side. In shape it is bluntly conical, with the apex about the fifth intercostal space. The base is on the level of the upper border of the third rib. It extends about | inch to the right of the ster- num, and approximately 3| inches to the left of the mid-sternal line. (Fig. 236.) The Pericardium.-The walls of the heart are made of cardiac muscle. It is covered by a layer of serous membrane which is doubled back to form a pouch-like structure. This sac has an outer fibrous investment which is attached to the diaphragm below, to the cervical fascia above, and to the pleurae covering the lungs on each side. This covering is the pericardium. It is applied loosely to the heart, and invests part of the large vessels leaving the heart. A serous fluid is secreted which serves to prevent friction, as the heart swings back and forth. The chambers of the heart are two ventricles and two auricles. The auricles are placed above the ventricles, and it is practically true to say there are two hearts, the right and the left, as they do not communicate with each other, though the auricles open into their corresponding ventricles. Leading out from the right ventricle is a large tube, the pulmon- ary artery, while the aorta leads out from the left ventricle. The 262 THE CIRCULATORY SYSTEM Fig. 236.-The pulmonary artery and aorta. The front part of the right lung has been removed, and the pulmonary vessels and the bronchial tubes are thus exposed. (Testut.) Fig. 237.-Cross-section through both ventricles, showing the shape of their cavities and the relative thickness of their walls. (Testut.) THE ANATOMY OF THE EEART 263 right auricle has opening into it two arge tubes, the superior and the inferior vena cavse. The left auric le has opening into it four pulmonary veins. There is much difference in the thickness of the wralls of the two ventricles, the left having the greater amount of tissue. This is required on account of the greate amount of work done by the left ventricle. (Fig. 237.) Fig. 238.-Left auricle and ventricle, the hind wall of each having been removed* (Testut.) Columnae Carnae.-The inner surface of the ventricle presents a series of fleshy projections. These are the columnae carnae. (Fig. 238.) They seem like additional supports to the walls. Valves of the Heart.-The openings between the auricles and ventricles, and those between the heart and its large vessels are closed by movable fibrous valves. These open to let the blood pass through, but close to prevent a backward flow of blood. On the right side of the heart, the opening between the right auricle and right ventricle is closed by the tricuspid valve. On the 264 THE CIRCULATORY SYSTEM left side, the corresponding valve is the mitral. The opening between the right ventricle and the pulmonary artery is closed by the pul- monary valve, with the aortic valve in the corresponding position on the left side. (Fig. 239.) Running between the auriculo- ventricular valves and the columme carme are delicate fibrous cords, the chordae tendinece. Lining the cavities and the valves of the heart is a delicate serous membrane, the endocardium. Fig. 239.-Valves of the heart and great arteries, viewed from above, the auricles having been removed. (Testut.) THE ANATOMY OF THE ARTERIES. Arteries are the tubes by which the blood is carried from the heart. The quality of the blood does not matter, that is, whether it is pure or impure, aerated or unaerated. If the vessel comes from the heart it is an artery. As the blood leaves the heart with considerable force, the arterial walls must be strong enough to withstand it. As it comes in spurts, the walls must be elastic enough to stretch and afterward recoil, returning to their normal size. The walls must provide for changes in the caliber of the vessel, so it may be made smaller on occasion. And, it must present no obstruction to the flow of blood by reason of roughness of the lining. To provide for all these contingencies, arteries have three coats, or tunics. On the outer side is a white fibrous layer, with some yellow elastic fibers. The middle coat has plain muscle tissue, with some yellow elastic tissue. The inner coat is an epithelial layer, with a small amount of yellow elastic tissue. The elasticity of the arterial walls is marked, especially in the larger ones. There is considerable variation in the relative amounts THE ANATOMY OF THE ARTERIES 265 of fibrous and muscular tissues, the largest arteries having little muscular but much fibrous tissue. The smaller arteries have more muscular and less fibrous material, while the middle sized arteries have about equal quantities of each. Divisions of an Artery.-From the heart, two large arteries are given off. These two divide and subdivide, branching in every direction like a tree. (Fig. 240.) As the arteries divide they become smaller, but when the cross-sections of all the branches are con- sidered, the sum total is much more than that of the original trunk. This is widening the bed of the arterial system, and as in any stream under such circumstances, the rate of flow is decreased. Fig. 240.-Diagram showing the branchings, anastomoses and confluence of arteries, (Gerrish.) In an artery which supplies an extremity, the trunk which enters the limb sends off branches from the side; it may send a deep or superficial branch that is as large as the original; it will send direct articular branches to the joints and recurrent branches going back to nourish the joint when the direct supply is shut off by muscular contraction or position; it will send off branches to anastomose with the anastomosing branches of other arteries, and send a nutrient artery to the bone. It will also send off small arteries to nourish the walls of the larger one, the vasa vasorum. When arteries have divided and subdivided until they are micro- 266 THE CIRCULATORY SYSTEM scopical in size, they have lost most of the fibrous covering, much of the muscular coat, but have retained all the epithelial tunic. They are then called "arterioles." (Fig. 241.) Arteries lie in a bed of areolar tissue, usually accompanied by the nerve that supplies the same part and the vein that drains it. Fig. 241.-Diagram of the arrangement of muscle cells in an arteriole. (Gerrish.) THE ANATOMY OF THE CAPILLARIES. When every coat of an arteriole is lost except the epithelial, it becomes a capillary. The single layer of epithelium forming the wall (Fig. 242), will allow the materials in the blood plasma to pass through it into the spaces around the microscopical cells, and the waste materials in the spaces to pass into the capillary. The length of a capillary is microscopical, and its diameter so small that the red corpuscles can pass through it in single file only. Their size Fig. 242.-Capillaries, showing the shape and arrangement of the cells which make their wall. (Carpenter.) varies, those in the lungs being the largest in the body. Those in muscle tissue are placed between the fibers in areolar tissue. When the capillary acquires a small amount of additional tissue, it becomes a venule, or venous radicle. This unites with another venule, and these with another, until several have united in a single vessel. Small veins unite to form larger veins, until finally two trunks dis- charge all the venous blood into the right auricle. The number of veins is greater than that of arteries, so that it is possible for the veins to contain all the blood in the body, leaving the arteries empty. THE ANATOMY OF THE LYMPHATICS 267 This is the condition that obtains after death. The rate of flow in the veins being slower than that in the arteries, more room is required to accommodate it. An artery is often accompanied by two veins, the "venae comities." THE ANATOMY OF THE VEINS. The veins are the tubes that carry blood to the heart. This holds good regardless of the state of the blood as to aeration. The walls of the veins do not need to withstand the shock of a force pump but they need to be as strong as those of an artery. They lack the stiffness of arterial walls and collapse immediately when emptied, whereas an artery remains patulous even if it is very small. There is considerable variation in the walls of veins. The inner coat is always the same, an epithelial layer, with minute folds in it called valves. These prevent the backward flow of the blood. As it starts backward, it runs in behind the folds of the valves and pushes them open, and thus closes the lumen of the vessel. (Fig. 243.) Fig. 243.-Valves of veins. A shows a vein cut open between the segments of two valves. B shows appearance of valves closed and open. (Testut.) The middle coat of the veins contains but little muscular tissue, but some fibrous material. The outer coat is white and yellow fibrous tissue. THE ANATOMY OF THE LYMPHATICS, INCLUDING GLANDS. (NODES.) Lymphatic vessels begin as the open ends of tubes in the spaces around the microscopical cells. These are "stomata" and the 268 THE CIRCULATORY SYSTEM spaces in which they open are variously termed, " perivascular," "intercellular," "juice channels," "juice canals," "lymph spaces." The lymph radicles unite to form larger tubes, which in turn unite to form still larger tubes, in the same manner as the veins. They decrease in number, but increase in size, though the lymphatics are not so large as the corresponding veins. The wall of the smallest lymph radicle is epithelial tissue only, but as they go on they take two other coats, very like those of the veins. The coats are so thin they are transparent. At very short intervals, the walls of the lymphatics are constricted by valves, formed by folds in the lining. (Fig. 244.) Fig. 244.-Lymph vessel laid dpen length wise, showing arrangement of valves. (Ger- rish.) Fig. 245.-A lymph node with its afferent and efferent vessels. (Testut.) Besides the tubes the lymphatic system includes nodes or glands. These are masses of lymphadenoid tissue in whose meshes are many white corpuscles. They sometimes have a fibrous capsule, and are easily identified. Sometimes they have no capsule, but are only infiltrated masses. (Fig. 245.) These nodes are plentiful in the neck, axilla, groin and abdomen. THE GENERAL CIRCULATION OF THE BLOOD. In an endless chain, it is difficult to select a place for breaking in. In the circulation of the blood through a system of closed tubes, THE GENERAL CIRCULATION OF THE BLOOD 269 one must start somewhere, though there is no beginning to be found. By reference to Fig. 246 and following the arrows as the description proceeds, a clear idea of the general circulation may be obtained. Starting with the left ventricle, the contraction of the heart throws blood into the aorta. The aorta sends off branches (systemic arteries) which divide and subdivide like the branchings of a tree, until the arterioles are reached, and then the capillaries in the body tissues (systemic capillaries). Fig. 246.-Diagram to show the course of the blood in passing from a given point through the two sets of capillaries to the starting-point. (Gerrish.) Then the capillaries become venous radicles, they in turn col- lecting into larger veins (systemic veins), until finally the stream passes into the right auricle. From the right auricle it goes into the right ventricle, and the contraction of the heart sends the blood into the pulmonary artery which divides and subdivides like the branchings of a tree, until the pulmonary capillaries are reached. These capillaries are in the lung 270 77IF CIRCULATORY SYSTEM structure and then the capillaries lead into veins, which unite into the pulmonary veins which pass the blood into the left auricle, from which it flows into the left ventricle, to start the journey again. The Pulmonary Circulation.-That part of the general circulation between the right ventricle and the left auricle is called the pul- monary circulation. The Systemic Circulation.-This includes the circulation from the left ventricle to the right auricle, and means a complete circuit of every part of the body, except the lungs. If a vertical line is drawn through Fig. 246, the right half colored blue and the left half colored red, it would show that the right heart deals with unaerated blood only, while the left heart deals with aerated blood only. THE GENERAL ARRANGEMENT OF THE ARTERIES. It is evident that the bloodvessels are everywhere in the body, since the smallest gash cannot be made through the skin without drawing blood. So wonderfully is the network of arteries arranged, if the direct blood supply of a part is cut off, there are other ways, through anastomosis by which the part may be supplied. Divisions of the Pulmonary Artery.-The pulmonary artery leaving the right ventricle divides into right and left pulmonary arteries, and breaks up in the lung substance, like the branchings of a tree, until the capillaries are reached. The exchange of O and CO2 occurs, and the formation of little veins begins, which join others, until there are four pulmonary veins that empty into the left auricle. Divisions of the Aorta.-The aorta is the largest artery in the body. It leaves the left ventricle and forms an arch toward the back and left. The first branches are two coronary arteries which provide nutri- tion for the heart itself. The large arteries that come off next supply the head, upper extremity and the walls of the chest. First, the innominate or brachio-cephalic arises on the right side, and imme- diately divides into the right common carotid and the right subclavian. Next, the left common carotid and the left subclavian arise from the arch (Fig. 236). The aorta now turns downward, and oppo- site the lower border of the fifth thoracic vertebra it becomes the thoracic aorta (Fig. 247). Continuing through the thorax it sends branches that supply the structures within the thorax and its walls. Reaching the diaphragm it passes through it and becomes the abdominal aorta. (Fig. 248.) Many large branches are given off which supply the viscera within the abdominal cavity, the diaphragm and the walls. At the level of the fourth lumbar vertebra, the abdominal aorta divides into the right and left common iliac arteries. A little further, at the level of the articulation of the last lumbar with the first sacral THE GENERAL ARRANGEMENT OF THE ARTERIES 271 vertebra, the common iliac divides into the interna and external iliacs. The internal iliac artery on each side goes into the pelvis and supplies the pelvic viscera and walls, the external genitals, the structures about the hip-joint and the inner part of the thigh. The Fig. 247.-Thoracic aorta. (Testut.) external iliac artery goes out of the abdominal cavity into the thigh, and becomes the femoral artery. (Fig. 249.) Coursing through the thigh, about two-thirds of the way down it becomes the popliteal artery, and keeps that name until it reaches the lower edge of the popliteus muscle, when it divides into the anterior and posterior tibial arteries. (Fig. 250.) 272 THE CIRCULATORY SYSTEM These arteries continue to the foot and are finally united plantar arches. (Fig. 251.) Fig. 248.-Abdominal aorta. (Testut.) Carotid Arteries.-Going back to the branches first given off, the common carotids divide into the internal and external carotids, as they pass up the side of the neck. (Fig. 252.) THE GENERAL ARRANGEMENT OF THE ARTERIES 273 The external carotid sends off various branches which supply the front of the neck, the face, scalp, pharynx and the external and middle ear. (Fig. 253.) Fig. 249.-Femoral artery. (Testut.) The internal carotid passes into the cranial cavity, sending off many branches, finally breaking up in the fissure of Sylvius. It supplies the brain and the eye. 274 THE CIRCULATORY SYSTEM Fig. 250.-Arteries in the dorsal part of the leg. (Testut.) Fig. 251.-Arteries in the sole of the foot. (Testut.) THE GENERAL ARRANGEMENT OF THE ARTERIES 275 Subclavian Artery.-Soon after starting, the subclavian artery sends off a branch, the vertebral. The two vertebrals unite, forming the basilar artery at the base of the brain. The basilar goes to the interior of the brain and anastomoses with the branches of the internal carotid. (Fig. 252.) Other branches of the vertebral are the internal mammary, the thyroid axis and the superior intercostal. Fig. 252.-Right subclavian and carotid arteries. The vertebral artery is seen threading the costotransverse processes of the vertebrae. (Testut.) The Axillary Artery.-The subclavius passes toward the outer side of the shoulder and opposite the lower border of the first rib becomes the axillary. The branches given off from the axillary go to the structures about the shoulder-joint. (Fig. 254.) At the lower margin of the teres major muscle, the artery enters the arm and becomes the brachial. Branches from it supply the muscles, the humerus, the shoulder- and elbow-joints and the skin over the arm. Just above the elbow, the brachial divides into the radial and ulnar arteries. (Fig. 255.) These pass down the fore- arm, sending branches to all contiguous parts, and finally meet in the two palmar arches, in the palm of the hand. (Fig. 256.) 276 THE CIRCULATORY SYSTEM The Thoracic Aorta.-The branches given off from the aorta while in the thorax are, the pericardial, the bronchial to the lung, the esophageal, the intercostals and the subcostal. Fig. 253.-Superficial arteries of the head. (Testut.) The Abdominal Aorta.-The abdominal aorta sends off a number of branches. Just below the diaphragm is a short trunk, the coeliac axis, from which the gastric artery for the stomach, the hepatic artery for the liver, and the splenic artery for the spleen pass off. These three main arteries branch and send off anastomosing vessels which supply the viscera in the upper abdomen. The suprarenal artery supplies the suprarenal glands. The superior mesenteric supplies the upper intestine, with the lower intestine supplied by the inferior mesenteric. The renal artery supplies the kidneys. Fig. 254.-Axillary and subclavian arteries. (Testut.) Fig. 255.-Arteries in the region of the bend of the elbow. (Testut.) 278 THE CIRCULATORY SYSTEM The ovarian artery supplies the ovaries. The phrenic artery supplies the diaphragm. The lumbar arteries go to the deep muscles of the back, Fig. 256.-Superficial palmar arch and its branches. Of the digitals, only the third is labeled. (Testut.) THE GENERAL ARRANGEMENT OF THE VEINS. The veins return the blood from the peripheral parts to the heart. They are in two sets, the superficial and the deep, with frequent communicating veins between the two sets. THE GENERAL ARRANGEMENT OF THE VEINS 279 Systemic Veins.-The deep veins usually accompany the artery and the same name is given to both, as the hepatic artery, hepatic vein. There are no. carotid veins, but the internal jugular drains the area supplied by the internal carotid. It joins the subclavian vein to form the brachio-cephalic or innominat ' on each side. The external jugular drains the external carotid artery area, emptying into the subclavian. (Fig. 257.) Fig. 257.-Veins of the neck and upper part of thorax, front view. (Testut.) The azygos veins form an anastomosis between the superior and inferior vena cavse. They receive the venous blood from the back and sides of the thoracic wralls. (Fig. 258.) The venous blood enters the right auricle by either the superior or inferior vena cava or by the coronary sinus. The latter comes from the substance of the heart. 280 THE CIRCULATORY SYSTEM The superior vena cava returns the blood collected from the head, neck, upper extremity and thoracic walls. The inferior vena cava from the lower extremity, the pelvis and the abdomen. Fig. 258.-Azygos and intercostal veins. (Testut.) The Portal Vein.-A peculiar arrangement of the circulation is the portal system. The veins from the stomach, intestine, spleen and pancreas unite to form the portal vein. This enters the liver, and breaks up into capillaries, and when the venous radicles are formed, they unite with those resulting from the hepatic artery, and pass out of the liver as the hepatic vein, going to the inferior vena cava. (See Fig. 296, p. 332.) THE GENERAL ARRANGEMENT OF THE VEINS 281 Superficial Veins of the Upper Extremity.-The superficial or sub- cutaneous veins lie between the layers of superficial fascia, and are visible under the skin. They occupy the areolar tissue network which holds the skin to the underlying structures. In the upper extremity the superficial veins form a network on the back of the hand, and a smaller network on the front of the Fig. 259.-Superficial veins of front of forearm and lower part of arm. (Testut.) wrist. Those on the back of the hand unite to form the radial vein which runs up the outer side of the forearm to just above the elbow where it joins the median cephalic to form the cephalic. (Fig. 259.) The posterior ulnar vein begins on the inner side of the network on the back of the hand, passes up to the elbow and there receives the anterior ulnar. This latter comes from the wrist along the inner side of the front of the forearm. These two ulnar veins form the 282 THE CIRCULATORY SYSTEM common ulnar vein which joins the median basilic to form the basilic. The median vein starts from the plexus on the front of the wrist, Fig. 260.-Superficial veins of the front of the leg and foot. (Testut.) Fig. 261.-Superficial veins of the front of the right thigh. (Testut.) goes to just below the elbow where it is joined by the deep median vein, and then divides into the median cephalic and the median basilic. GENERAL ARRANGEMENT OF LYMPHATICS AND NODES 283 The cephalic runs up the outer side of the front of the arm, to the axillary, into which the basilic also empties. Superficial Veins of the Lower Extremity.-These veins have numer- ous valves to prevent the force of gravity interfering with the onward progress of the blood toward the heart. There are two main venous trunks, internal and ex- ternal, which begin in a network over the instep and on the dorsum of the foot, called the dorsal plexus. This was formed by the veins from the toes, the inner and outer bor- ders of the foot. Long Saphenous Vein.-The internal or long saphenous vein begins at the inner part of the dorsal plexus (Fig. 260), passes up the inner side of the thigh nearly to Poupart's ligament, and there enters the femoral vein. It passes in front of the internal malleolus, and back of the internal condyle of the femur, and is joined by many superficial veins and numerous branches from the deep veins of the sole, leg and thigh. It contains from seven to twenty valves. (Fig. 261.) Short Saphenous Vein.-The external or short saphenous vein begins at the outer part of the dorsal plexus, passes behind the external malleolus, and then on the outer and back part of the leg to the lower part of the pop- liteal space, where it joins the popliteal vein. It is joined by superficial veins from the foot, heel and back of the leg. It communicates with the internal saphenous, and has from nine to fourteen valves. (Fig. 262.) THE GENERAL ARRANGEMENT OF THE LYMPHATICS AND THE NODES. The lymphatic ducts are similar to small veins in that they are very small at the begin- ning, until by uniting with others, large trunks are formed. The ducts in the right upper half of the body, the right side of the head, the heart, neck, chest, upper extremity and the upper surface of the liver, are all drained into the right lymphatic duct, which enters the right subclavian vein at its junction with the right internal jugular. All other parts of the body drain into the Z/zoraczc duct. Fig. 262.-Superficial veins of the dorsum of the leg. (Testut.) 284 THE CIRCULATORY SYSTEM The Thoracic Duct.-This begins in the abdomen just in front of the spine, on a level with the second lumbar vertebra. An expanded pouch, the receptaculum chyli, receives the contri- butions from the surrounding digestive organs, and then the duct passes upward to the level of the fourth thoracic vertebra (a dis- tance of from 15 to 18 inches), and there enters the left subclavian vein at its juncture with the left internal jugular. (Fig. 258, p. 280.) Fig. 263.-The lymph nodes of the neck and upper part of the thorax. (Testut.) The diameter of the duct is about that of a goose quill. Double valves guard the openings of both the right lymphatic and the thoracic ducts to prevent any regurgitation of lymph. Collections of nodes are found in the neck, axilla, groin and abdomen, wherever deleterious substances are most apt to need fighting by the lymph corpuscles, i. e., the white corpuscles or phagocytes. (Figs. 263, 264, 265.) Fig. 264.-The nodes and vessels of the upper limb. (Testut.) Fig. 235.-Mesenteric nodes. (Testut.) 286 THE CIRCULATORY SYSTEM THE PHYSIOLOGY OF THE CIRCULATION. The blood is the fluid that is carried to all parts of the body and which carries in itself the nutrient material needed by every cell, the waste products from the working cells and the secretions of the ductless glands. The heart sends out about 4 ounces of blood at every contraction, or every .86 second, or an average of 72 times a minute. This is the rate for the majority of persons, but individuals may have a more or less rapid rate within the limits of perfect health. Young children have a more rapid pulse, and the aged are apt to have it slower. During exercise and digestion the rate is increased. Systole and Diastole.-Blood is sent from the heart by the con- traction of the cardiac muscle, rhythmically, with periods of rest. The contractions constitute systole, the rest periods, are diastole. The Cardiac Cycle.-The contraction may be likened to a circular wave that starts in the upper part of the heart, in the auricles, at the entrance of the large veins, and passes downward to the lower part of the ventricles. After the auricles become filled with blood from the vena cavse and the pulmonary veins, their systole begins, forcing the blood into the ventricles, through the auriculo-ven- tricular openings. This occupies about .16 second, after which their diastole occurs, until it is time for the next contraction. Immediately following the auricular is the ventricular systole in which the blood is thrown into the aorta and pulmonary artery. This lasts .30 second, after which the ventricular diastole lasting .40 second occurs. At the beginning of the auricular systole, the valves between the auricles and ventricles are open, while those between the ven- tricles and large arteries are closed. At the beginning of the ven- tricular systole, the mitral and tricuspid valves close, the aortic and pulmonary open. During diastole of the ventricles, all the valves are closed. This prevents regurgitation of blood into the ventricles from the arteries and allows the auricles to fill. This alternation of systole and diastole is the cardiac cycle. The Innervation of the Heart.-The heart receives two sets of nerve fibers. The vagus conveys inhibitory impulses which slow or stop the contractions, while the other set derived from the sympathetic ganglia accelerate them. There is also a set of sensory fibers which in certain pathological conditions register pain. The balanced action of the inhibitory and accelerator fibers determine the rate of the heart beat. But, there is also an automatic element involved in which the stimulus which excites the activity of the heart arises within itself instead of being brought to it. Whether there are intrinsic nervous ganglia in the heart itself is not fully determined. THE PHYSIOLOGY OF THE CIRCULATION 287 Apex Beat.-The rhythmic contraction of the heart may be felt by placing the hand about its own width from the center line of the chest, at the level of the fifth interspace, or if the breasts are not pendulous, about | inch below the nipple, on the left side. The heart swings forward and slaps against the chest wall, so the impulse can be felt, and sometimes seen. The Pulse.-Other places where the effect of the heart's systole can be observed are where a fair-sized artery comes near the surface. At the side of the neck, at the radial side of the front of the wrist, etc., this impulse, called the pulse may be felt. In the neck it is synchronous with the apex beat, but is a little later at the wrist, and still later in the arteries farther off. It will be noted that the pulse does not present quite the inter- mittent character of the apex beat, but is remittent. That is, there is a continuous flow of blood, but rhythmic waves of greater force are present. Steadying the Output of the Heart.-The blood leaves the heart in spurts, going into the aorta and pulmonary artery, but in the smallest arteries and capillaries, the flow is ster.dy without any waves. This change is due to "arterial recoil." Arterial Recoil.-The aorta contains much elastic tissue, so that it is easily distended as the blood is thrown into it at each ventric- ular systole. When this impulse is over, the walls recoil, press- ing down upon the blood, and imparting a steady push to it. As the aortic valve is closed, the blood cannot go back to the heart, and must go toward the periphery. The larger arteries contain a greater amount of elastic tissue than the small ones do, so this pressure of the walls continues for some distance from the heart, making the flow more steady. This pressure upon the blood in the arteries is called arterial tension, and it is subject to various influences which increase or decrease it. The wave induced by the heart's systole is lost in the small arteries, and in the capillaries, so the flow is steady and slow. As the blood goes out into the "arterial tree," there is more resistance to its onward flow, due to the narrowing of the tube. This is " peri- pheral resistance," and this is increased or lessened by muscular contraction or relaxation. The greater the resistance, the harder the heart has to pump to send the blood to its destination, with consequent increase in arterial tension. Some other factors that increase tension or blood-pressure, are, standing, walking or running, as compared with sitting or lying; mental strain, and very hearty meals. Cold baths increase while full tepid baths decrease the pres- sure. Strong emotions increase the pressure. The pressure during systole is lowest in children, gradually increasing as the years advance until it becomes relatively high in the aged. Whether this is due to a gradual hardening of the artery 288 THE CIRCULATORY SYSTEM walls is open to discussion, as the less elastic these walls are the greater is the rise in systolic pressure with every heart beat. But, as high blood-pressure occurs in early middle life in some cases, there are evidently many causes still unknown. The secretion of some of the ductless glands is a potent influence, one way or another. The Suction Pump.-So little force has the blood in the capillaries, or in the neighborhood of the ultimate tissue cell it would simply stay there indefinitely, unless some force could carry it along. The force pump has lost its effect, but a suction pump is now developed which returns the venous blood to the heart. It is developed by the respiratory movements, the changing size of the heart, muscular contractions and joint movements. During inspiration, the diam- eters of the chest increase, producing a potential vacuum. This sucks the air into the lungs from outside, and sucks the blood into the chest and heart from other parts of the body. The blood so drawn in must be venous, as the strong action of the heart sends the arterial blood in the opposite direction. The inspiratory movement also draws the lymph from the periphery, as the lymph vessels are connected with the venous system. A considerable amount of suction is exerted by the relaxation of the heart, drawing the blood from the vena cavae and pulmonary veins into the auricles. There are many opportunities for the development of vacuums in the veins, as the blood is in this system of closed tubes. If a vein is pressed upon, the walls collapse, the blood is forced from under the pressure, and when the pressure is removed, a vacuum results. The blood that was pressed out has had but one direction in which it could go, forward, as the valves prevent its backward movement. The blood must rush forward to fill the vacuum, so the net result of the pressure on the vein is to carry the venous blood toward the heart. Every muscular contraction, with the broadening of the muscle produces pressure on the vessels contained in its substance, with suction. A part of the body in which the muscles are not used becomes, as it were, "water-logged," with nothing to start the venous blood and lymph toward the heart. By reason of the attach- ment of the deep fascia to the large veins at the joints, movement of the latter pulls upon the veins, and increases suction. By these means, the force pump on the arteries, and the suction pumps on the veins and lymphatics, the blood gets around the body, making a complete circuit every twenty-two seconds. Quantity of Blood in Body.-The quantity of blood is about 7 per cent of the body weight. This approximates 10 pints in an average man. It is not enough to furnish every part with a full supply all the time. If the muscles and skin have plenty, there is not sufficient for the digestion of a hearty meal, or to allow much effective brain work. THE PHYSIOLOGY OF THE CIRCULATION 289 Fortunately, the glandular organs have alternating periods of work and rest. When they work, they require a large supply of blood, which goes to them through the vasomotor nerves acting in harmony with the secretory nerves of the sympathetic. These organs are usually supplied by the middle-sized arteries that have considerable muscle tissue in their walls. Their caliber is readily decreased by the vasoconstrictors or increased by the vasodilators, thus lessening or increasing the blood supply. When the muscles are in vigorous contraction, much blood is needed by them and by the skin, and their demand is more insistent than that of even the digestive organs. The process of digestion may be suspended by hard muscular work soon after eating. This alternation of full blood supply to the different parts keeps the blood on the move and improves its quality. The Work of the Lymph.-The lymph vessels contain lymph, a colorless fluid which is the plasma of the blood after it has leaked through the walls of the capillaries into the spaces surrounding the tissue cells, plus the material coming from the cells. This material includes all kinds of secretions as well as waste. This fluid after the cells have taken what they need must go back into the blood- vessels. The venous capillaries cannot take it all up, so the open stomata of the lymph radicles must do it. Physiologists are not agreed as to just how this is done, but it is done, and the surplus lymph goes through the lymphatics to the venous system. During inaction, there is little flow, but when the venous suction pumps pull, the flow becomes active. The peristaltic action of the muscles of the intestine moves the lymph in that region. The lymph nodes serve to strain out of the lymph certain delete- rious substances. In them the white corpuscles, or at least, some of them, seem to originate. The Work of the Red Corpuscles.-Some of the red corpuscles are formed in the red marrow of the bones, but it is open to question if that is the only source for their production. Their chief constituent is hemoglobin, which gives the red color to the blood. It is a form of organic iron, which has a strong affinity for oxygen. In the lungs the hemoglobin takes oxygen from the air and carries it in the blood stream to the tissues. The cells take it and by a process of oxidation use it, producing some form of energy and carbon dioxide. The latter is carried by either the red cor- puscles or plasma to the lungs to be eliminated. The Work of the White Corpuscles.-This has been the subject of much investigation. All white corpuscles are not alike. The two main groups are leukocytes and lymphocytes. The leukocytes wander about, but the lymphocytes seem unable to do so. It is probable the white corpuscles protect the body from pathogenic bacteria and other foreign organisms. The formation of substances 290 THE CIRCULATORY SYSTEM in the blood which immunize the body to infection is thought to be the work of the white corpuscles. They aid in the absorption of fats from the intestines and also of peptones. They may take some part in the coagulation of the blood, and help maintain the normal supply of proteins in the blood. The Blood as a Carrier.-The plasma is involved in serving as a common carrier between the various parts of the body. Among the substances carried are oxygen, carbon dioxide, water, nitrogen, various proteins as fibrinogen, paraglobulin, and serum albumin. Substances called extractives, as fats, sugars, urea, uric acid, creatin, jecorin, glycuronic acid, lecithin, cholesterin and lactic acid are also present. The mineral salts, include combinations of chlorine, carbon, sulphur and phosphorus with sodium, potassium, magnesium and iron. And, yet more. Enzymes, the internal secretions, immune bodies, complements and opsonins, and, prothrombin and anti- thrombin. With such a complex organization, the plasma gives up different substances to different cells and receives a supply of other material to carry around, either to be used by other cells, expelled from the body as waste or used to stimulate the functions of other parts. Clotting.-Some of the materials in the blood are concerned in causing the blood to clot when the wall of a vessel is injured so the blood escapes. Clotting is Nature's way of stopping a hemorrhage, by catching the red corpuscles in a fibrinous network, and forming a solid plug at the open end of the bloodvessel. Apparently the platelets are involved in this process, as well as fibrinogen and possibly white corpuscles. Thrombin seems to be a constituent of the antecedent of fibrin which is fibrinogen, without which clotting does not occur. Certain persons, "bleeders," seem to lack this substance, so their blood fails to clot after injuries to the bloodvessels. QUESTIONS. Describe the heart, and make a diagram of it. Compare the structure of an artery and a vein with reference to the work done by each. What is the relation of capillaries to cells? How do lymphatics begin? Why should two sets of bloodvessels be needed to return blood to the heart, when one set is sufficient to carry it from the heart? What is the pulmonary circulation? What is the portal circulation? Trace the course followed by a red corpuscle in going from the right auricle to the palm of the left hand. Trace the course going from the left ventricle to the right kidney. What parts of the body are drained by the inferior vena cava? QUESTIONS 291 What area is drained by the long saphenous vein? What area is drained by the portal vein? By the hepatic vein? By the internal jugular vein? Describe the thoracic duct. What is the "cardiac cycle?" How is the intermittent flow of blood from the heart changed to the steady flow, with waves, in the arteries? What work is done by the blood plasma? What work is done by the red corpuscles? What work is done by the white corpuscles? What is "arterial tension?" How does the blood get back to the heart from the capillaries? CHAPTER IX. THE RESPIRATORY SYSTEM. Respiration may be defined as an exchange of gases, of which the object is to provide oxygen for the combustion in the tissues and to remove the products of combustion in the form of carbon dioxide. As with other vital processes of the body, the essential action of respiration takes place in the microscopical tissues, and the entire mechanism is so arranged. The process may be divided into two parts, external respiration, during which the air external to the body is carried to the lungs, and the exchange occurs between the blood in the capillaries of the pulmonary arteries and the air in the alveoli; and internal respira- tion which occurs in the ultimate tissues with the exchange between the blood in the systemic capillaries and the tissue cells. THE ORGANS CONCERNED IN RESPIRATION. The passages through which the air passes to the microscopical tissue cells, are in order, The nose (mouth). Posterior nares (naso-pharynx). Pharynx. Larynx. Trachea. Bronchi. Bronchioles. Alveoli. The Nose.-The nose is a prominent feature of the face, and varies in shape according to the race and the climatic conditions under which the race has developed. Tropical races have rather flat noses, with short air passages, while races living in colder regions develop longer air passages with more prominence of the nose. The nasal bones are short and small, forming the " bridge of the nose," and to them is attached a cartilaginous addition that provides for movement of the nostrils and takes up the force of external blows to a considerable extent. Small muscles are attached to the nose providing for facial expression and extra efforts in breathing. The nose is lined with mucous membrane containing many "goblet cells," and having a rich blood supply. This membrane does not cover the small surface only that is visible on cursory 292 293 THE ORGANS CONCERNED IN RESPIRATION inspection, but is continued over a large area by covering the " tur- binated bodies." These are three in number, on each side, and their convoluted shape gives a large area of warm mucous membrane over which the air passes on entering the nose. The air can thus be warmed before it reaches the more delicate structures beyond.1 The Posterior Nares.-Through the posterior openings of the nose, the way leads into the naso-pharynx, on the wall of which is a mass of adenoid tissue. When this tissue becomes hypertrophied, the condition known as " adenoids" develops, with interference with the easy ingress of air, and consequent normal development of a child (Figs. 234 and 235). The Pharynx. -The pharynx is the space at the back of the mouth, and is divided into the naso-pharynx above, the oro-pharynx, opposite the tongue and the laryngo-pharynx, just above the larynx. It is 5 inches long, and on the posterior wall are two openings which are the beginnings of the Eustachian tubes for carrying air to the middle ear. On the outside of the pharynx are a number of muscles that con- strict its caliber, forcing the bolus of food, after mastication, from the mouth into the esophagus. It is lined with a continuation of the mucous membrane of the nose, mouth, middle ear and larynx, but ciliated epithelium to the level of the hard palate provides for the waving outward of mucus and its easy removal. The Larynx.-Opening from the pharynx below, are two aper- tures, the esophagus and the larynx, and except during the act of swallowing, both are open at all times. When a bolus of food passes into the esophagus, a trap-door closes over the larynx to prevent food going into it. This door is the epiglottis. The Epiglottis.--The epiglottis is a thin triangular leaf-like piece of cartilage, attached to the base of the tongue and to the upper and anterior part of the larynx. Its action is involuntary, but when the coordination of the muscles of the pharynx and those attached to the epiglottis becomes impaired, it may fail to close over the larynx and food may enter the latter. This will cause choking, and violent efforts at coughing it out. If the material enters the trachea it may entirely block the ingress of air. The appearance of the larynx is that of an irregular box made of four pieces of cartilage, and the muscles and ligaments that hold them together. The cartilage keeps the lumen open, and the mus- cles on the outside are concerned in swallowing, respiration and phonation. Over this box-like structure, at the upper end pass two bands of fibrous tissue, covered with mucous membrane. These are the 1 Under the description of the nerve of smell, additional details are given of the nose. 294 THE RESPIRATORY SYSTEM Fig. 266. Laryngeal cartilages and ligaments from behind. (Testut.) Fig. 267.-Laryngeal cartilages and ligaments from in front. (Testut.) THE ORGANS CONCERNED IN RESPIRATION 295 vocal cords. They are so placed as to leave a triangular opening which varies in width or which may be entirely closed. This open- ing is the glottis. The variation of size provides for the passage of more or less air, according to circumstances. The air coming from the lungs sets the vocal cords in vibration, causing sound. The glottis may be closed at the end of inspiration to prevent the expiration of air and give fixation of the diaphragm in connection with the muscles of the abdominal wall to produce compression of the viscera below, as in defecation, micturition and vomiting. It may also be closed to fix the chest and give greater power in muscular efforts, such as lifting, jumping, etc. It is to be noted that by the voluntary closing of the glottis at the beginning of inspira- tion, the suction effects of the inspiratory movements can be increased. Fig. 268.-Larynx, viewed from above. (Testut.) The Trachea. (Fig. 269.)-The trachea is the next part of the respiratory tract and consists of a tube about 4| inches long, made of fibrous tissue in which is imbedded incomplete cartilaginous rings whose function is to keep the tube patulous. The back of the trachea lies in contact with the esophagus, and on that surface the cartil- aginous rings are lacking so as not to interfere with the passage of food. The Bronchi.-The trachea divides into two branches that go to the right and to the left into the lungs, and are called the primary bronchi. These are large tubes with cartilaginous rings throughout their circumference, and are lined with a mucous membrane con- tinuous with that of the larynx. The bronchi divide into smaller 296 THE RESPIRATORY SYSTEM tubes (bronchial tubes) which continue dividing and subdividing until the diameter becomes very minute. The cartilage in the walls continues until the tubes become as small as in diameter. These tiny tubes are the bronchioles and they vary in size between and Jyy of an inch. Throughout these air passages ciliated epithelium is present. Fig. 269.-Trachea and bronchi, front view. (Testut.) Alveoli.-Each bronchiole opens into a collection of 8 to 16 alveoli, or air vesicles, called a lobulette, and it is here the actual work of external respiration occurs. The alveoli are from y-g- to -g-g-g- of an inch in diameter, with walls of a single layer of flat epithelial cells with elastic fibrous tissue. The area covered by their walls is esti- mated at 90 square meters, or more than a hundred times the area of the skin of the body. Ramifying among the vesicles are the capillaries of the pulmonary arteries. In these microscopical tissues are the two single layers of epithe- lial cells through which gases may pass freely, according to the amount of pressure exerted by each gas. THE ORGANS CONCERNED IN RESPIRATION 297 The Lungs.-The ramifications of the tubes with the alveoli and the areolar tissue holding them together constitute the lungs. In shape they are two irregular cones, contained in the thorax, with the bases resting on the diaphragm and the apices reaching into the neck about 1| inches above the clavicles. (Fig. 236.) The Mediastinum.-The mediastinum separates the two lungs, and includes all the space in the thorax not occupied by the lungs. It extends from the sternum to the spinal column, and from the upper opening of the thoracic cage to the diaphragm. Four divisions are made, the superior, anterior, posterior and middle mediastinum. The superior is above the pericardial sac; the anterior in front of the same; the posterior behind, and the middle which is occupied by the pericardial sac and its contents. Fig. 270.-Right lung, outer surface. (Testut.) In the superior and posterior mediastinums are important organs, as the trachea, esophagus, thoracic duct, vagus and other nerves and the great vessels connected with the heart. The heart encroaches on the space occupied by the left lung. The lungs are covered by a sheet of serous membrane, the visceral layer of the pleura, which is reflected upon the chest wall, lining it. This forms the parietal layer of the pleura, which is ordinarily in contact with the visceral layer. A small amount of fluid is secreted which lubricates the surfaces. The right lung is divided into three lobes, the left lung into two lobes. Each lobe is divided into a number of small areas, | of an inch in diameter, called lobules, and these are collections of lobu- lettes. (Fig. 271.) The lungs are always close to the inner wall of the chest, and their shape changes with changes in the diameters of the thorax. Fig. 271.-Diagram of a lobule of the lung. A bronchiole is seen dividing into two branches, one of which runs upward and ends in the lobule. In the lobule are four groups of infundibula. At the left are two infundibula the alveoli of which present their outer surfaces. Next are three infundibula in vertical section, the alveoli of each opening into the common passageway. Upon the ultimate bronchiole of this group are alveoli. In the next group the first infundibulum shows a pul- monary, arteriole surrounding the opening of each alveolus, and the second gives the same with the addition of the close capillary network in the wall of each alveolus. The same arrangement of vessels is seen in the alveolus upon the bronchiole of this group. Around the fourth group is a deep deposit of pigment, such as occurs in old age, and in the lungs of those who-inhale coal-dust and the like. On the bronchiole lies a branch of the pulmonary artery (blue), bringing blood to the infundibula for aeration. It also supplies nourishing blood to the tubes and other structures within the lobule. Beginning between the infundibula are the radicles of the pulmonary vein (red), a root of which lies upon the bronchiole. The bronchial artery is shown as a small vessel bringing nutrient blood to the bronchiole (outside of the lobule), the artery and vein, and all of the structures between and around the lobule. No attempt is made to show the sustentacular tissue which occupies the spaces within and around the lobule. (Gerrish.) THE ORGANS CONCERNED IN RESPIRATION 299 Conversely, changes in the shape of the lungs produces changes in the diameters of the thorax. The Thorax.-The thorax is a cone-shaped cage, partly bony, partly cartilaginous and partly muscular, which contains the two lungs, the heart, the large bloodvessels, the esophagus, thoracic duct, various nerves and glands. (Fig. 272.) Fig. 272.-Relations of lungs (red) and pleurae (blue) to the front walls of chest. (Testut.) The cavity of the thorax is closed, and shut off from the abdominal cavity as well as from the outside, but the interior of the lungs com- municates with the outside air by means of the trachea, etc. The atmospheric pressure, thus affects the interior of the lungs, but the walls of the chest prevent it from influencing the outside of the lungs. If the chest is punctured, the lungs immediately collapse on account of the equalization of the pressure outside and within. When the air enters the lungs, the expansion produced causes them to fill the entire cavity, except where there are other structures. When air leaves the lungs, the chest walls follow the shrinking lungs, and the thoracic cavity is made smaller, but the lungs still completely fill it. There is no vacant space, permanently, in either case. 300 THE RESPIRATORY SYSTEM Normal Position of the Thorax.- The position of the thorax changes continuously during life, but the position at the end of a passive expiration may be considered essentially normal, and form- ing a starting point from which to estimate the degree of inspiration and expiration. Any enlargement of the thorax from this norm may be considered an active inspiration. Any diminution of the size may be considered an active expiration. A return to the norm after an active inspiration, is a passive expiration and is not caused by muscular effort but by the recoil of the lung tissue after expansion. THE MECHANISM OF RESPIRATION. Respiration may be said to begin with the movement of inspira- tion, in which the diaphragm contracts and increases the diameter of the thorax from above downward. At the same time, the lower ribs are pushed outward, unless the inspiration is forced, in which case they tend to be drawn inward. It is possible the quadratus lumborum and serratus posticus inferior muscles hold the lower ribs from being drawn inward during inspiration. At the same time the diaphragm is contracting, the scaleni and the external intercostal muscles contract and turn the ribs upward and outward, increasing the diameters of the thorax laterally and from before backward. These changes in diameter would create a vacuum if the air did not rush to fill the space. If the glottis is open it does fill the entire space so there is no room between the lungs and the chest walls. The glottis may be closed voluntarily while the chest diameters are being enlarged, with an increase of the physiological effects of inspiration. (See Kellogg's Treatise on Massage, in connection with visceral lifting.) When the diaphragm contracts, the central tendon descends, pressing upon the abdominal contents, and the abdominal wall bulges out. If the front wall of the abdomen is prevented from bulging, the pressure is transmitted downward, mainly to the pelvic cavity. Following the contraction of the diaphragm and other muscles, comes their relaxation, with an upward push of the dome of the diaphragm and a recoil of the lung tissue which pushes the air out of the lungs, in expiration. Under ordinary conditions, inspiration is active, expiration is passive. When inspiration is forced, expiration becomes so to some degree. Active inspiration and passive expiration is called evpnea. Forced or labored respiration is dyspnea, with the prefix of inspira- tory and expiratory, according to which ever is forced. During forced respiration, all the muscles attached to the ribs, all that THE MECHANISM OF RESPIRATION 301 hold the scapula firm, and all that fix the abdomen may be called into activity. Types of Respiration-These are distinguished according to the parts of the trunk that are especially involved. When the abdominal wall is pushed forward in inspiration, the breathing is called dia- phragmatic, or abdominal. When the respiration is mainly carried on by the action of the ribs, increasing the lateral and antero- posterior diameters, with little movement of the diaphragm, it is called costal breathing. This type results from the constriction of the waist. Those who have never worn anything to do this have abdominal respiration as a rule. The rhythm of respiration is about 18 times a minute, or | the rate of the heart beat. This rate increases or decreases with that of the heart and temperature. Inspiration and expiration follow each other with no interval between them, though on account of the passive nature of expira- tion it seems as though it were much shorter than inspiration. After every six to ten respirations there usually comes one that is distinctly deeper and longer. Ordinarily the depth of respiration varies with its rapidity, faster in shallow, slower in deep breathing. Ratio of Rate of Respiration, Pulse and Temperature.-The nor- mal ratio between pulse and respiration is 4 to 1. With a normal temperature of 98.6° F. the pulse is 72, the respirations 18 per minute. With each increase of 1 degree in temperature, the pulse increases 10 beats, the respirations 2|. Sounds of Respirations.-By applying the ear to the chest wall in different localities various respiratory sounds may be heard. Below the clavicle or over the scapula, with each inspiration a sound is heard as of a gentle breeze in distant tree-tops. This sound is pro- duced by the air going into the alveoli, and it is called the "vesic- ular murmur." Listening over the middle of the back, the inspired air is passing through the bronchi, and the sound is higher pitched and as though one should blow over the mouth of a bottle. These are the two sounds possible in health. Relation of Respiration to Circulation.-While the exchange of oxygen and carbon dioxide is the outstanding fact in respiration, there are other very important features connected with it. In the Chapter on the Circulation reference was made to the suction exerted on the venous blood by the action of the lungs. This is brought about by the difference between the pressures within the thorax and that within the abdomen during respiration. Intrathoracic and Intrapulmonary Pressure.-The space between the lungs and chest walls is practically nil, except during inspiration, but there is a space between the two lungs, the mediastinal space. The pressure exerted upon the contents of this space is the intra- 302 THE RESPIRATORY SYSTEM thoracic pressure, or it is the pressure exerted upon the heart, large vessels, thoracic duct, etc. The pressure in the interior of the lungs, which communicates with the atmosphere, or the intrapulmonary pressure, is that of the atmosphere. During inspiration, when the thoracic cage increases in all its diameters, so that it is temporarily larger than the contained lungs, the intrapulmonary pressure falls temporarily below that of the atmosphere, or is minus, as the air becomes more or less rarefied, according to the amplitude and rapidity of the inspirations, and the size of the opening to the outside. At the end of inspiration if there is a pause, the pressure rises again to that of the outside atmosphere. During expiration, the collapse of the chest walls from the relaxa- tion of the muscles of inspiration takes place rapidly enough to compress the air somewhat as it goes out, and a temporary rise of pressure occurs. When the glottis is closed and a strong inspiration taken, the intrapulmonary pressure is much lowered, but if the glottis is closed and an expiration is made, the pressure is so much increased it may prevent the emptying of the vena cavse and pulmonary veins into the auricles. This effect may be observed in the appearance of congestion in the face and neck during violent coughing, straining at stool or supreme muscular efforts of any kind. Under normal conditions the pressure upon the mediastinal space is negative or minus, for the walls of the thorax are interposed between that and the outside air. If the lungs are fully expanded they are a greater bar to the pressure of the atmosphere, and the intrathoracic pressure becomes more largely a minus quantity than when the lungs are compressed in expiration. But, it is always negative. Given, therefore, the outside atmospheric pressure exerted on the large veins in the neck and axilla through the skin, and the negative pressure in the mediastinal spaces, the venous blood is bound to go in the direction of the least resistance, that isj into the heart. Intra-abdominal Pressure.-The pressure within the abdomen varies according to inspiration and expiration. In inspiration, the diaphragm presses down upon the abdominal viscera, the walls of the abdomen, unless flaccid, resist the outward pressure, with the net result of increased intra-abdominal pressure. This forces the blood from the inferior vena cava into the thoracic part of the vessel, where the pressure is negative. Thus the suction pump acts on the blood from the lower extremities, pelvic and abdominal regions. The Relation of Respiration to Abdominal Functions.-The only action of the diaphragm is in inspiration, but that is rhythmic. Below' the diaphragm are the stomach and intestines, in whose walls are THE COMPOSITION OF INSPIRED AND EXPIRED AIR 303 smooth muscle tissue. The health of these organs depends upon their functional activity and this is directly aided by the respiratory movements of the diaphragm in exerting a massage action upon them. An intermittent pressure, which is the essence of massage, stimulates the circulation and the peristaltic movements of the abdominal viscera. If the respiration is mainly costal, this stimulation is lacking, and the viscera are very apt to sag and function feebly. Pulmonary Capacity.-This indicates the total amount of air con- tained in the lungs, and is about 330 cubic inches. Vital Capacity.-Vital capacity is the quantity of air that can be exhaled after making the largest possible inspiration. It can be measured by means of a spirometer, and though subject to error is fairly accurate as a means of testing one's available lung power. A spirometer consists of a graduated cylinder resting in a tank of water. The cylinder is counter-balanced by a weight which allows it to move up and down in the water with the least resistance. A tube passes from outside up into the cylinder chamber, through which the air is blown, so as to cause the cylinder to rise and indi- cate its amount. The vital capacity of an average-sized individual is about 230 cubic inches, or 3700 cc. This amount is greater in tall persons, in those with very flexible chest walls, and where the occupation calls for vigorous respiration. Variations in the reading may be due to lack of understanding of the technic involved, inability of the subject to carry out instructions, or to defects in the instrument. Residual Air.- It is impossible to expel all the air from the lungs, by any effort. That remaining is the residual air, about 100 cu. in. Tidal Air.-With each quiet respiration, there is a change of some 20 cu. in. This is the tidal air. Complemental Air.-Complemental air is the amount that can be taken in by a forced inspiration. It is about 110 cu. in. Supplemental Air.-Supplemental air is the amount that can be forced out by effort and is about 100 cu. in. THE COMPOSITION OF INSPIRED AND EXPIRED AIR. Atmospheric air in general consists of 20.96 volumes of oxygen, 79 of nitrogen, 0.04 of carbon dioxide, a variable amount of watery vapor, a small amount of organic material, ammonia, dust, nitric acid, etc. It varies in temperature from 20° F, below zero to 115° F. above, in the temperate climes, with further extremes possible. The tem- perature is modified by passing through the nostrils, so it is more nearly 70° F. when it arrives at the lower air passages. 304 THE RESPIRATORY SYSTEM Expired air has undergone certain changes. Oxygen is 16.02 volumes, nitrogen is 79, CO2 is 4.38, and it is saturated with watery vapor at a temperature of 98.6° F. There has been a decrease in oxygen of 4.94 and an increase of carbon dioxide of 4.34 volumes. More oxygen has been lost than shows in the carbon dioxide, but it is supposed some atoms of oxygen have combined with hydrogen and formed water. Body heat is lost by this elimination of water after its conversion from a liquid to a gaseous state. It does not seem possible to say just how much carbon dioxide is necessary to make air unfit to breathe. A proportion of 4 per cent in a confined place causes definite symptoms of distress, but a fairly good rule is to try to get out of air that has an offensive smell to one just coming from fresh open air. THE EXCHANGE OF OXYGEN AND CARBON DIOXIDE. There are three forces effecting the exchange of these elements. 1. The movements of inspiration and expiration. 2. The changing size of the heart. 3. The diffusibility of gases. The first two forces result in the variation of intrapulmonic and intrathoracic pressure, which causes the alternate ingress of air rich in oxygen and the egress of air charged with CO2. The diffu- sibility of gases effects the exchange in the alveoli and in the micro- scopical cells of the body. In a mixture of gases, each presses according to its volume. When oxygen has 21 volumes, it presses into the lungs with more force than when it has but 16 volumes, as in expired air. If a membrane is interposed between two gases of different volumes, that with the higher pressure would go through until the pressure is equalized on both sides of the membrane. In the lungs, this permeable membrane is the single layer of epithelial tissue in alveolar and capillary walls, and through this the oxygen is going from the outside. The red corpuscles load up with it. When the carbon dioxide arrives with a pressure of 4.38 it goes through the membrane because the CO2 in the atmospheric air has less pressure, so the CO2 is expelled. The arterial blood passes to the tissues nearly saturated with oxygen. In the systemic capillaries the pressure of O is much greater than is that in the cells, so it is given off to the cells. In the cells, CO2 is constantly being formed and its pressure is higher than in the blood and lymph in the neighborhood. It therefore passes into the blood and is carried off. THE INNERVATION OF RESPIRATORY MOVEMENTS 305 THE INNERVATION OF THE RESPIRATORY MOVEMENTS. The diaphragm is supplied by the phrenic nerve, and branches of the cervical and brachial plexi supply the other muscles of inspira- tion, while branches of the lumbar plexus supply the abdominal wall. The facial nerve supplies the nose, and the vagus, the larynx. The muscles concerned are all voluntary, so respiration may be increased or decreased at will. But, the ordinary movements occur without conscious control through centers in the medulla. This center is apparently self-sufficient and sends out the impulses that coordinate the muscles concerned. The rate is varied according to the needs of the organism. It may be that the accumulation of carbon dioxide in the blood serves as the stimulus to the center in the medulla, but, the normal rhythm of 15 to 18 per minute goes on, day and night, waking or sleeping. Muscular activity, emotions, sleep and temperature vary the respiratory depth and rate. QUESTIONS. What is respiration and where does it take place? What is the mediastinum? What is " intrathoracic pressure?" What is " intrapulmonary pressure?" What are the boundaries of the lungs? In what way does the oxygen of the air get to the tissue cells? How does the CO2 produced in the body get out? What is the relation of respiration to circulation? * What is the relation of respiration to digestion? Describe vital capacity. How does expired air differ from inspired air? CHAPTER X. THE DIGESTIVE SYSTEM. THE COMPOSITION OF THE BODY. Various parts of the body have been considered as to their form and structure. It has been shown that all the diverse forms of which the body is composed may be placed into five classes of tissue cells. These tissue cells may again be examined to see of what elements they are composed, and it is found that the same elements are present in each in varying amount and arrangement. Considera- tion has been given to the combination of organs that form the mechanism by which the substances of which the cells are made may be carried to them for their up-building, repair and functioning. Another mechanism provides for the gaseous requirements of the cells. With both the above mechanisms the blood is the purveyor of the substances needed by the cells, air, water and food. These must be taken into the blood before they can serve the cells. Air and water are ready for immediate use, but food must undergo many processes before it can become a part of the blood. Food is needed for growth and repair, and to maintain the heat of the body and its energy. Of all the materials needed, the most vital is air. Without it, we would die in a few minutes. There is more air available in the world than anything else. The next in urgency is water, as without that, death ensues in a few days. The least urgent of the three is food, as persons have gone six weeks without food and survived. The indication for the need of water is thirst, which is usually located in the mouth and throat, but water in the mouth does not relieve thirst. Water introduced into the circulation will. The sensation of hunger for food is referred to the stomach, but hunger is felt if the stomach is removed, and the sensation is relieved by feeding per rectum. It is thus seen that hunger and thirst are the calls of the tissue cells for food and drink. The amount of food, drink and air needed varies greatly according to the surrounding temperature, activity and age of the individual. 306 THE COMPOSITION OF FOODS 307 THE COMPOSITION OF FOODS. Of foods there are many, but on analysis they are found to con- sist in varying proportions of Water. Mineral matter. Carbohydrates. Fats. Protein. The body is made up of these same elements (see the Composition of the Plasma in Chapter VIII.). Water.-This forms about 70 per cent of the body-weight. It acts as a solvent in the body and renders materials capable of absorption. It is a constituent of every tissue, and is in every kind of food, in varying proportions. Besides the amount taken in an ordinary diet, about 3 pints daily are considered necessary. This may be increased or decreased according to the activity, temperature and food taken. Mineral Salts.-There are twelve so-called tissue salts present in the body. Upon their correct proportion and balance hangs much of the health and efficiency of the organism. These salts are: The phosphates of magnesium, iron, calcium, sodium and potas- sium; the chlorides of sodium and potassium; fluoride of calcium; silica; sulphates of calcium, sodium and potassium. These are found in appreciable quantities in the various tissues, as: In the nerve cells, phosphates of magnesium, sodium, potassium and iron. In muscle cells, phosphates of magnesium and potassium, with sodium, iron, and chloride of potassium. In connective tissue cells, silica. In elastic tissue cells, fluoride of calcium. In bone cells, fluoride of calcium, phosphates of magnesium and calcium. In cartilage and mucous cells, chloride of sodium. Sulphur, iron, carbon and phosphorus are never free but always combined with organic materials. The most abundant of these salts are chloride of sodium or com- mon salt and phosphate of calcium. Various forms of malnutrition follow the absence of these salts from the dietary. They should always be left in the food, though modern methods of refining frequently result in robbing it of these necessary elements. Carbohydrates.-These substances consist of carbon, hydrogen and oxygen, in which the hydrogen molecules are always double those of oxygen, or in the proportion to form water, as C6Hi2O6. 308 THE DIGESTIVE SYSTEM Fats.-These are compounds of the same elements, but the oxygen elements are much fewer than the others, as in C5iH98O6. Proteins.-Proteins or proteids are substances in which the con- stituents are carbon, hydrogen, oxygen and nitrogen. They are more stable in their composition than the others, and exist in a variety of forms. THE NEED FOR REPAIR AND REPLACEMENT OF MATERIALS. The cells of some organs have relatively long resting periods between the working periods. Others have only momentary times for rest. But, whether they are actively at work or practically resting, the life processes involve a constant breaking down of the tissue cell. The fact that an animal given adequate water but no food pro- gressively loses weight is sufficient evidence of a constant need for repairs and replacement of materials in the living body, varying according to the activity undergone. The carbohydrates and fats break down in producing heat and other forms of energy, and the proteins that have been used in the framework of the cells break down by use, just as the parts of a house do in the process of time. These substances are replaced by food and no substitutes have yet been discovered for it. The food we eat is converted into the bodies we use. . THE PROCESSES IN CONVERTING FOOD INTO THE HUMAN ORGANISM. It is interesting to observe the history of the food that is going to be made into a human being, and study the relationship between the methods of procuring food in these modern times and the neces- sity for taking formal gymnastics or learning to play games. In the primitive races, food meant either the chase, the laborious tilling of the soil or the care of flocks and herds, except in the tropics where food grew with little effort on the part of man. A piece of meat to eat had to be cut from an animal; perhaps, the animal had to be caught and killed; the wood for the fire to cook it had to be gathered; the water in which it was cooked had to be carried from the spring. No matches being available, fire was made by laborious processes, and perhaps stones had to be heated and rolled into the pot to heat the water enough to cook the meat. The head of the family that attended to getting such a meal did not need to go to "gym" classes to keep/i7. Now, the specialization of work of modern days is seen. We decide to have chops for dinner, and a telephone order to the butcher 309 THE CHEMICAL CHANGES IN DIGESTION shop bring the articles to the kitchen door. A match to the gas- stove broiler, and attention to the matter for rather less than ten minutes makes the chops ready to eat. Have we the appetite that primitive family had for their meat? Does it taste as good and does it digest as well as for that other family? But, then how many people helped us get our chops? How many'were concerned in the telephone; in the stock farm that raised the lamb; in the stock yards, where it was prepared for market; in the making of the retail butchers' shop; in the motor cars that delivered it; in making the gas for fuel and the stove for burning the gas; the salt and pepper that seasoned the chops, and the dishes from which it was eaten? If the above processes are elaborate they are not more so than the various stages through which food passes before it becomes a part of our structure. These processes may be grouped as: 1. Prehension or taking the food in the hands to put it in the mouth. 2. Mastication, or chewing by which it is divided and subdivided into small particles. 3. Deglutition or swallowing, which passes it along from the grinding room to the next station. 4. Gastric digestion, or the mechanical and chemical changes that it undergoes in the stomach. 5. Intestinal digestion, or the mechanical and chemical changes it undergoes in the intestine. 6. Absorption or its taking up by the lymphatic vessels to be carried to the venous system, and then to the heart. 7. Cell assimilation, or the building-up into the cell structure, which is the final step by which food becomes truly a part of one's self. Foods which cannot yield energy are not affected chemically, but are dissolved if not already in solution, and discharged from the body in the same state as when received. Food which yields energy must be separated from the innutritious parts, and go through various changes. THE CHEMICAL CHANGES IN DIGESTION. These are effected by the presence of certain substances called "enzymes." Various observers have given different definitions to this term. Oppenheimer suggests the following: "An enzyme is a substance produced by living cells which acts by catalysis. The enzyme itself remains unchanged in this process, and each enzyme exerts its activity only upon substances whose molecules have a certain definite arrangement." 310 THE DIGESTIVE SYSTEM Enzymes act to the best advantage at the body temperature, but are destroyed in a high temperature. They never completely con- vert the substance upon which they act. If these substances are removed as fast as formed, the enzyme keeps on acting. Enzymes are divided into many classes according to the sub- stances acted upon by them. The principal of these, according to the food affected, are: 1. The proteolytic or protein-splitting enzymes. They cause a hydrolytic splitting of the protein molecule. 2. The amylolytic or starch-splitting enzymes. They cause a hydrolytic splitting of the starch molecule. 3. The lipolytic or fat-splitting enzyme. 4. The sugar-splitting enzymes. Two groups of these, one of which converts the double sugars into the single sugars or mono- saccharids; the other splits the monosaccharids. 5. The coagulating enzymes which convert soluble into insoluble proteins. Of the above group the proteolytic enzymes include: Pepsin, in the gastric juice, which converts proteins into peptones and proteoses. Trypsin, in the pancreatic juice, which splits proteins into their constituent amino-acids. Erepsin, in the small intestine, which splits peptones and pro- teoses into their constituent amino-acids. The amylolytic enzymes include: Ptyalin, in the saliva, which converts starch to sugar (maltose). Amylase, in the pancreatic juice, which converts starch to sugar (maltose). Liver glycogenase, in the liver, which converts glycogen to dex- trose. Muscle glycogenase, in the muscles, which converts glycogen to dextrose. Invertase, in the small intestine, which converts cane sugar to dextrose and levulose. Maltase, in the small intestine, saliva and pancreatic juice, which converts maltose to dextrose. Lactase, in the small intestine, which converts lactose to dextrose and galactose. The fat-splitting enzymes include: Lipase or Steapsin, in the pancreatic juice, fatty tissues, blood, etc., which splits neutral fats into fatty acids and glycerin. The hydrolytic action of an enzyme consists of a molecule of the affected substance, in the presence of an enzyme, taking up water and subsequently splitting the new molecule into two or three simpler ones. THE ORGANS CONCERNED IN DIGESTION 311 THE ORGANS CONCERNED IN DIGESTION. THE ALIMENTARY CANAL AND ACCESSORY ORGANS. The process of digestion is begun in the mouth and finished in the small intestine. To all intents and purposes the alimentary canal may be considered as a tube passing through the body from the mouth to the anus, and the food in it should be considered as outside the body until it is taken up from the tube by absorbent vessels. The alimentary canal begins with the mouth, it continues through the esophagus, stomach, small intestine and large intestine. Acces- sory organs to the canal, are the teeth, tongue, salivary glands, gastric glands, intestinal glands, liver and pancreas. These will be considered in order, before taking up the kinds of food presented to them for preparation. The Mouth.-This is an irregularly oval aperture, formed by the superior maxillary bone, the mandible and the cheeks, and limited and closed in front by the lips. Its floor is formed by the tongue. It communicates posteriorly with the pharynx, and superiorly with the naso-pharynx. It contains the teeth and the tongue and has opening into it the ducts from three pairs of salivary glands. It is lined with mucous membrane, which with the salivary secre- tion keeps the mouth moist and aids in the appreciation of taste. Articulate speech is assisted by the mouth and its accessories. This cavity serves as a chamber in which mastication and insalivation of food can take place. The cheeks by the contraction of the muscles in their walls help to move the food around, and the lips keep it from falling out of the mouth. The hard palate forms the roof of the mouth with the soft palate attached to its posterior border. Dangling from the center of the soft palate is a process called the uvula. (Fig. 273.) This is con- cerned in articulation. The imperfect development of the palate bones, resulting in what is known as "cleft palate" or "hare-lip" is a serious impediment to speech. The Teeth.-These are hard white structures set in the margins of the superior maxilla and the mandible. They are for biting, tearing and grinding the food, the different groups having these special uses. The teeth grow in two sets, one in infancy, the other in childhood and youth. The first set is superseded by the second, and so is called the temporary or milk teeth. The second set is called the permanent teeth. In the first set are 5 teeth in each half of each jaw, or 20 in all. Beginning at the middle line, there are 2 incisors, 1 canine and 2 312 THE DIGESTIVE SYSTEM molar teeth. They begin about the seventh month, and the full 20 are usually erupted by the end of the twenty-fourth month. About the sixth year a molar tooth develops, which is the first of the permanent set. It is called the "six-year molar." About the Fig. 273.-The soft palate and tonsillar regions. (Testut.) Fig. 274.-The teeth of the right half of the upper jaw in their sockets, viewed from below. (Gerrish.) THE ORGANS CONCERNED IN DIGESTION 313 seventh year the temporary set begins to be shed and is replaced by the permanent teeth. The 2 molars of the milk set are replaced by 2 bicuspids of the permanent set. The third molar is not developed until late adolescence and is popularly called the "wisdom tooth." (Fig. 274.) The temporary teeth are replaced by the permanent set at about the following years. First molar, sixth year. Two middle incisors, seventh year. Two lateral incisors, eighth year. First bicuspids, ninth year. Second bicuspid, tenth year. Canines, eleventh to twelfth year. Second molar, twelfth to thirteenth year. Third molar, seventeenth to twenty-first year. Fig. 275.-The jaws of a child of seven and a half years, the external table of bone having been cut away to show the stage of second dentition. (Testut.) The replacement of one set by the other occurs by the later- coming teeth in their growth absorbing the roots of the milk teeth, until only the crown remains. Little force is then needed to remove that. (Fig. 275.) 314 THE DIGESTIVE SYSTEM Parts of a Tooth.- A tooth is composed of three parts, crown, root and neck. The crown is the part that projects from the gums; the root is imbedded in the alveolar process of the jaws; and the neck is the slightly constricted part that is just under the gums. (Fig. 276.) The crown is composed of dentin, covered with enamel. Enamel is a form of epithelial tissue with the cells calcified and is the hardest material in the body. The root tapers and fits into the bony sockets very neatly, so as to avoid uneven pressure. In the tooth is a central cavity or pulp chamber. The pulp con- sists of a nerve (branch of the trifacial or fifth) bloodvessels and cells in an areolar mesh. The sockets of the teeth are lined with a form of periosteum, called the pericementum, which is reflected on to the root of the tooth as far as the neck. Fig. 276.-Diagram of the structure of a tooth. The Uses of the Teeth. -Teeth aid in phonation and add to the attractiveness of the features, as well as helping to preserve the contour of the face. The front teeth are for cutting food, while the back teeth serve as grinders. The surfaces of the upper molars fit in with those of the lower jaw, each tooth being in contact with two opposite ones. The lower jaw moves on the upper in a side to side, antero-posterior and an up-and-down movement. Various muscles attached to the jaws, the hyoid bone and the temporal bone are concerned in these movements. This grinding or mastication is aided by the tongue, lips and cheeks, which with the saliva to moisten the food, initiate the process of digestion. The more thorough the mastication, the more finely the food is divided, the better can the digestive juices get at it. The Tongue.-The tongue is a muscle, very mobile, changing in length and width at every contraction. It is an organ of the special sense of taste; an organ of speech, and assists in mastication, insaliva- tion and deglutition. It is about 3| inches long, covered with mucous membrane under which is a layer of fibrous tissue. 315 THE ORGANS CONCERNED IN DIGESTION The upper surface is rough by reason of many papillae. Their size varies, the smaller ones being in front, and a few (8 to 12) large ones or circumvallate papilloe, toward the back. (Fig. 233.) Most of the taste-buds are found in these circumvallate papillae. The nerve supply, other than the gustatory nerve, is from the fifth and twelfth cranial nerves. There are many nerves of ordinary sensation in the tongue, so it is very sensitive. It gives information to the brain as to the size of the mass in the mouth and the stage of mastication reached. Fig. 277.-The salivary glands. The right half of the body of the mandible has been removed. GL. W., gland of Weber; GL. B., gland of Blandin. (Testut.) Salivary Glands.-There are three salivary glands on each side. The parotid, largest in size, is beneath and in front of the lobe of the ear. The submaxillary is below the mandible, near the angle of the jaw. The sublingual is under the mucous membrane of the mouth lateral to the middle line in front. 316 THE DIGESTIVE SYSTEM These glands all have ducts which open near the teeth, their secretion, saliva, being mixed with that from numerous mucous glands of the mouth. Their flow is increased by mastication and by the smell of appetizing food. (Fig. 277.) Saliva not only moistens the food, but it contains the digestive ferment, ptyalin. This ferment begins the digestion of the starches of the food. The more thorough the mastication and insalivation of the food, the more nearly is the starchy element digested. Saliva also aids in the appreciation of taste by keeping moist the tongue and mouth, and in phonation by the same means. The dry tongue cleaves to the roof of the mouth and one is speechless in consequence. The Tonsils.-Though the tonsils have no special relation to the digestive process, they will be considered here as connected with the mouth. The tonsils are two ovoid bodies of varying size at the entrance to the pharynx between the anterior and posterior pillars of the fauces. (Fig. 273.) They are a collection of lymph nodules, covered by a capsule of fibrous tissue which sends trabeculae into its substance and divides the tonsils into many compartments. The surface next the fauces has 12 to 15 depressions or crypts which extend into the tonsil. Mucous glands open into these crypts and with their secretion is mingled great numbers of lymph cells. The function of the tonsils is not understood. Apparently, they absorb and destroy pathogenic bacteria, if they are in a healthy condition, but if enlarged and hardened they seem to be a source of infection themselves. In the fevers of children they become con- gested and enlarged. It is possible their protective function may end at the age of puberty, at which period a child becomes less liable to the infectious fevers. Deglutition.-After the food has been thoroughly masticated and insalivated, deglutition follows with almost no effort. If the pre- ceding processes have not been well performed, there must be a definite muscular effort to swallow the bolus of food, which is done by the aid of the constrictor muscles of the pharynx. (Fig. 278.) The Esophagus.-The esophagus is a tube, 9 inches long, | to | of an inch in diameter, which extends from the pharynx to the cardiac orifice of the stomach, passing through the diaphragm on its way. It lies behind the trachea. The coats of the esophagus or gullet are muscular and epithelial. The upper part of the muscular coat is of striated muscle, therefore under the control of the will. Further down there is a mixture of striated and plain muscle while at the lower part, only plain muscle tissue is found. The movements of the middle and lower parts are involuntary THE ORGANS CONCERNED IN DIGESTION 317 and vermicular, moving the bolus of food toward the stomach. From this point, the work of digestion is carried on below the dia- phragm or in the abdominal cavity. Only a few of the organs in the abdomen are not concerned in digestion. Fig. 278.-Muscles of the pharynx, viewed from behind, together with the associated vessels and nerves. (Modified from Testut.) The Abdominal Cavity.-The abdomen is the cavity in the lower part of the trunk, between the diaphragm above and the brim of the pelvis below. 318 THE DIGESTIVE SYSTEM It is bounded in front and on the sides by a muscular wall which includes the rectus abdominis, obliquus externus abdominis, obliquus internus abdominis, and the transversalis muscles. On the posterior lateral walls are the quadratus lumborum, psoas magnus muscles and the iliac fossa, while the vertebral column is posterior. The dome of the diaphragm extends as high as the fourth rib, varying according to the respiratory movements. The shape of the abdomen varies according to age and sex. In infancy, it resembles an inverted, truncated cone. The adult female is the reverse, with the male type more barrel-shaped with a flatten- ing antero-posteriorly. The cavity is lined with serous membrane, called the peritoneum. This is reflected on to the viscera and enables the different organs to slip and slide a short distance without friction. The organs con- tained in the cavity are: The stomach, liver, spleen, pancreas, 2 kidneys, 2 suprarenal bodies, the small intestine, the large intestine (except the rectum), abdominal aorta, and its branches, the inferior vena cava, the beginning of the thoracic duct, the vagi, besides numerous lymph nodes. For convenience in describing the struc- tures contained in the cavity, the abdomen is divided into nine regions, though anatomists are not agreed as to the boundaries of them. Following the arrangement described in Gerrish's Anatomy, two transverse planes cut the abdomen. One of these is at the level of the tenth costal cartilage, the other at the level of the anterior- superior iliac spines. This forms three zones, the subcostal above, the umbilical in the middle and the hypogastric below. These zones are divided by two sagittal planes passing through the middle of Poupart's ligament. Thus the abdomen has the umbilical region around the umbilicus, the right and left lumbar on either side of it. The epigastric region is above the umbilical, with the right and left hypochondriac on either side. The hypogastric is below the umbilical, with the right and left iliac or inguinal on either side. Apparently this leaves nothing in the hypochondrical regions, but it should be remembered that the diaphragm comes upward, so there is a greater space than appears on the surface. (Fig. 279.) The Stomach. -The stomach is a pear-shaped viscus, located in the epigastric and left hypochondrium. Food enters it at the cardiac orifice, just below the diaphragm to the left of the middle line of the body, and leaves it from the pyloric orifice somewhat lower down and to the right of the middle line. Between these two orifices, superiorly, the line of curvature of the stomach is called the " lesser curvature." The long way around, between the two is the "greater curvature." (Fig. 280.) These curvatures mark the line of attachment of the peritoneum, front Fig. 279.-Regions of the abdomen according to the method of Gerrish Fig. 280.-Stomach and duodenum, the liver and most of the intestines having been removed. The pyloric end of the stomach should be represented as turned directly backward. (Testut.) 320 THE DIGESTIVE SYSTEM and back. At the lower part there is given off a double fold of peri- toneum, which falls down like an apron over the intestines. It passes down from the stomach and doubles back, wrapping the transverse colon. This is the great omentum. It contains more or less fat, sometimes a great quantity of it, and protects the mass of intestines, especially from cold. The stomach is variable in size, according to its contents. When empty the anterior and posterior walls are in contact with each other. When it is distended, its greatest length is about 14 inches, its transverse diameter 5 inches, and its capacity is some 5 pints. Fig. 281.-Diagram to show the direction of the fibers in the three muscular layers- (Testut.) The stomach is nearly vertical when empty. When distended the pylorus is moved 2 inches toward the right and the greater curvature is tilted toward the front. It exerts considerable pressure upward on the diaphragm, with more or less consequent interference with the action of the heart. The Coats of the Stomach.- Four coats invest the stomach, the serous or peritoneum, the muscular, the submucous and the mucous. Muscular Coats. -The muscular coat varies in thickness from of an inch over the cardiac end to yj of an inch at the pylorus. It consists of three layers of unstriated muscle. The outer layer is longitudinal, the middle layer circular, and the inner layer oblique in direction. (Fig. 281.) The muscular fibers increase in thickness at the pyloric end so they form a thick ring-like sphincter called the pylorus. THE ORGANS CONCERNED IN DIGESTION 321 The Submucous Coat.- This is a layer of loose-meshed areolar tissue, in which the larger bloodvessels and nerves are imbedded, protecting them from pressure and allowing free movement between the muscular and mucous coats. Mucous Coat.- This is of an inch thick, consisting of columnar epithelium, resting on a basement membrane. The mucous mem- brane is divided into numerous polygonal depressions from the bottom of which extend gastric glands. (The honey-comb tripe of the markets illustrates these depressions in a larger way.) Gastric Glands.- The gastric glands are tubular and secrete the gastric juice which contains pepsin, rennin and HCl. The glands nearest the pyloric end secrete mostly pepsin, while those at the fundus (large end), secrete both acid and pepsin. (Fig. 282.) Gastric Juice.- The gastric juice is a thin, almost colorless fluid of acid reaction, and a specific gravity of 1003 to 1005. Free hydro- chloric acid is produced to the amount of about 0.2 per cent to 0.3 per cent, to make the secre- tions and stomach contents acid. As soon as food is put into the mouth the flow of gastric juice begins. In twenty-four hours from 3 to 7 pints are made. Action of Pepsin.-The enzyme, pepsin, which is a proteolytic ferment, acts only in an acid medium. It converts proteins into such forms that they will pass through an animal membrane, that is, it can go through the wall of a capillary, lymphatic or cell. In the digestion of proteins, the first step is to syntonin; then to a primary proteose; then to a secondary pro- teose; then to a peptone, and finally to amino- acids and peptids. Amino-acids are the units or building stones out of which the protein molecule is con- structed. They are the final product obtained when proteins are hydrolyzed. There are a number of different kinds of these fundamental forms. When proteins have been reduced to their simplest constituents they may be assimilated by the cells after absorption. Rennin.- The second enzyme in the gastric juice, rennin, coagu- lates soluble proteins, as the casein in milk. After coagulation, casein is insoluble and is acted upon by pepsin in the same manner as are the other proteins. Why this is neces- sary is a matter for conjecture. Fig. 282.-Cardiac gland in longitudinal section. (Gerrish.) 322 THE DIGESTIVE SYSTEM The gastric juice does not act upon carbohydrates nor fats, except to dissolve the envelope in which the fat is encased. In order to keep the gastric juice in contact with all the food, the muscles of the stomach keep up a churning movement, in which the food particles move back and forth and seemingly are thrown against the pylorus with force, until they have been sufficiently digested to pass through. The rhythmic contraction of the stomach walls constitutes peri- stalsis. Gastric digestion lasts from two to five hours, but the pro- teins are only partly digested when they leave the stomach, except such albuminoids as gelatin which are completely converted. Chyme.- When the stomach contents are ready for going out to the next laboratory, the mixture is called chyme. It is of about the consistency of pea-soup, with minute particles of food suspended in a liquid. Fig. 283.-A loop of small intestine, showing the mode of distribution of the arteries, (Testut.) The Small Intestine.-Leaving the stomach through the pyloric orifice, the chyme passes into the first part of the small intestine. For about 10 inches this is the duodenum. The rest of the small intestine makes up a total length of some 20 feet. This is divided into two parts, the jejunum and the ileum. No distinct boundary separates these parts, but the first 8 feet is usually accepted as the jejunum. The small intestine is a tube, averaging about 1| inches in diameter and laid in the middle of the abdomen in a series of apparently tangled loops. At its distal end it opens into the caecum, the begin- ning of the large intestine. It is held in place by the mesentery, or folds of peritoneum. (Fig. 283.) Coats of the Small Intestine.- There are four layers in the walls of the small intestine, a serous, a muscular, a submucous and a mucous coat in the order named from without inward. THE ORGANS CONCERNED IN DIGESTION 323 The serous coat is the peritoneum. This starts from the anterior surface of the vertebral bodies as a sheet of tissue. It envelopes the tube and then goes back to the vertebral bodies. This forms a smooth, slippery covering for the intestine and anchors the coils firmly, so they may move freely but still hold in place. The mus- cular coat is in two layers, one longitudinal and the other circular. The submucous coat is of areolar tissue with a network of blood- vessels, nerves and lymphatics imbedded in it. The mucous coat on the inner surface presents a velvety appear- ance and many ridges. The ridges are the raZrwZcr conniventes, which increase the working surface of the tube and hold the food in con- tact with the digestive juices for a longer period. Villi.- The velvety appearance is due to some 4,000,000 to 10,000,000 villi. These are organs of absorption. They are less than of an inch in height and of an inch in diameter. (Fig. 284.) Fig. 284.-Free surface of the mucous membrane of the small intestine, showing villi, solitary glands and openings of the intestinal glands. Semidiagrammatic. (Testut.) The villi are conical or cylindrical in shape with a lymph radicle in the middle. (These are special lymph vessels called lacteals). Around the lacteal is a network of capillaries, some unstriated muscle fibers and a mass of nucleated cells. The whole is covered by columnar epithelium. (Fig. 285.) Crypts of Lieberkuhn.- In the mucous membrane are many tubular glands (crypts of Lieberkuhn) which secrete the succus entericus or intestinal juice and mucus. Lymph Nodules.- In the walls of the intestine are small bodies that are similar to lymph nodes. These are solitary glands, and 324 THE DIGESTIVE SYSTEM their work is related to that of the nodes in the mesentery. (Fig. 285.) The Duodenum. --1The 10 inches of intestine that is called the duodenum, performs a very important part in digestion. Fig. 285.-Mucosa of small intestine in ideal vertical cross-section. (Testut, after (Heitzmann.) The duodenum winds around the head of the pancreas (Fig. 286), and receives a secretion from that organ, from the liver, and from its own peculiar glands (Brunner's glands) (Fig. 287). These are mixed with the chyme and act upon it chemically. The pancreatic juice is a colorless fluid, strongly alkaline, in reaction. When mixed with the chyme the acidity acquired in the stomach is neutralized so the food is then either alkaline or neutral. The enzyme pepsin ceases its action on this change of reaction, but the pancreatic juice supplies four enzymes which require a neutral or alkaline condition. They are trypsin, amylase, steapsin, and a rennet-like substance. In addition to these enzymes, erepsin is secreted by the glands in the intestine. 325 THE ORGANS CONCERNED IN DIGESTION Fig. 286.-The duodenum, its four parts marked a, b, c, d. The liver is lifted up; the greater part of the stomach is removed, broken lines indicating its former position. (Testut.) Fig. 287.-Duodenal gland. (Frey.) 326 THE DIGESTIVE SYSTEM The trypsin and erepsin act on the protein bodies, finishing their conversion to amino-acids. The amylase completes the digestion of the starches. Steapsin acts on the fats and with the help of the bile forms soaps or emulsions that can be absorbed. The bile from the liver is of a dark greenish-red color, bitter in taste and odorless. It helps in the emulsification of fats, promotes intestinal peristalsis, inhibits putrefaction in the intestinal tract and promotes the absorption of fats. In the jejunum and ileum the enzymes that change cane sugar and other sugars into absorbable sugars, are produced. Carbonate of soda is also one of the products of the small intestine, serving to neutralize the acidity of fatty acids. Movements of the Small Intestine.- The muscular movements of the small intestine as seen under the roentgen-rays, is a kind of segmented division. A portion of the tube seems to undergo a chopping motion, then the peristaltic wave carries the food along to another loop, where the chopping begins again. The food has now become chyle, and is of a milky appearance. It is taken up along the entire route by the lacteals in the villi and .the capillaries. The lacteals carry the newly absorbed food to the receptaculum chyli, the beginning of the thoracic duct, whence it goes to enter the great veins in the neck. The capillaries carry it to the veins that enter the liver, as the portal vein. ACCESSORY ORGANS TO THE DIGESTIVE TRACT. There are two organs in the abdomen that are accessory to the alimentary tract, the liver and the pancreas. The Liver.-The liver is in the upper right quadrant of the abdomen, extending to the left beyond the middle line. It is the largest gland in the body, weighing between 3 and 3| pounds. It is wedge-shaped with the greatest width 8 to 9 inches, its height 6 to 7 inches, and its antero-posterior diameter 4 to 5 inches. The base of the wedge is to the right. It is of soft solid consistency, friable and a dark reddish-brown in color. The liver is divided by five fissures into five lobes. The left and right lobes are primary divisions, but the right lobe is subdivided into the quadratus, spigelii, and caudatus. The fissures give passage to blood- vessels and one of them is the bed of the gall-bladder. (Fig. 288.) The liver is attached to the under surface of the diaphragm, and to the anterior wall of the abdomen by folds of peritoneum. It is covered with a fibrous membrane, which forms a capsule. The substance of the liver is made up of small units of structure called lobules. These are held together by areolar tissue and by the rami- fications of the portal vein, hepatic artery, hepatic vein, bile ducts, lymphatics and nerves. THE ORGANS CONCERNED IN DIGESTION 327 The Lobule.- This is the working part of the liver, the laboratory in which the numerous functions of the liver take place. They are small granular bodies about to yy of an inch in diameter, with irregular outlines. The lobules have in the center a small vein which issues from it, carrying the collected blood from the portal vein capillaries and those of the hepatic artery. Around this vein the hepatic cells are grouped in radiating columns, as closely packed as possible, leaving room only for the capillaries of the portal veins, the bile ducts and nerves on the sides. The cells are abundantly supplied by the portal vein with material which includes newly digested food. From this, bile is manufactured and given off to the small ducts on the sides of the cells. Fig. 288.-The liver, lower surface. (Drawn from the His cast.) (Gerrish.) Blood also comes to the lobule by way of the capillaries of the hepatic artery. This supply is mainly concerned with the nutrition of the lobule itself. The venous capillaries which arise after the lobule is supplied carry off the blood which has come in through the portal vein, by way of the hepatic vein to the vena cava. Besides making bile, the liver cells work over the nitrogenous waste of the blood into a new substance called urea. This is really an internal secretion of the cells, as it does not pass off through ducts as the bile does, but goes back into the blood. Still a third function of the liver cell is the storage of glycogen. Glycogen is a form of sugar which comes from the digestion of carbohydrates, though sometimes from that of proteins, and which is to be burned in the cells as fuel to 328 THE DIGESTIVE SYSTEM produce heat and energy. The need for fuel is more or less constant, but the digestive process occurs at intervals only, usually three Fig. 289.-Portal system of veins. The liver is turned upward and backward, and the transverse colon and most of the small intestines are removed. (Testut.) times a day, consequently the necessity for a storehouse, from which a supply may be doled out to meet the hourly need. The liver cells THE ORGANS CONCERNED IN DIGESTION 329 are this storehouse, with a supply ready to be taken up by the blood and carried to the parts where it is used. Glycogen could also be considered as an internal secretion, since it passes back into the blood instead of into a duct. Gall-bladder. - In the process of digestion, bile is used, being poured out in the duodenum on the entrance of the food from the stomach, of an acid reaction. The bile so used has been stored in the gall-bladder, following its previous formation. The small ducts of the right lobe unite into a large duct; those of the left lobe do the same, and the two ducts form one large vessel, the hepatic duct. Many of the ducts open directly into the gall-bladder. Here the Fig. 290.-The cystic duct in section, with part of the gall-bladder, hepatic and common bile ducts. (Testut.) bile is stored until needed, when it passes down out of the bladder through the cystic duct. The cystic duct unites with the hepatic duct to form the "ductus communis choledochus," or common bile duct. This opens into the duodenum about 4 inches beyond the pyloric end of the stomach. The gall-bladder is about 4 inches long, pear-shaped, and holds about 1 ounce, ft is on the under surface of the front edge of the liver. (Fig. 290.) The Pancreas.-This is a large gland in the upper part of the abdomen, behind the stomach. It is somewhat hammer-shaped, with the head embraced by the duodenum. It is about 6 inches long, 1| inches wide and from | to 1 inch thick. (Fig. 291.) 330 THE DIGESTIVE SYSTEM It is pinkish in color and weighs between 2 and 3 ounces. The structure of the pancreas is that of a compound tubular gland. The tubes are coiled in small masses called lobules, with the cells short and conical. (Fig. 292.) Fig. 291.-The pancreas, dorsal view. The head is seen in the embrace of the duodenum. The portal vein and superior mesenteric artery lie behind the neck. (Drawn from the His cast.) (Gerrish.) „ The gland is similar to the salivary glands in its work, secreting pancreatic juice which passes out through the duct of Santorini into the duodenum (Fig. 293). Fig. 292.-Cross-section of pancreatic acini. (Testut.) This gland has other cells than those concerned in the production of pancreatic juice. The so-called "islands of Langerhans" have to do with forming an internal secretion which profoundly influences nutrition. Death from inanition in two or three weeks follows the removal of the pancreas. The failure of its internal secretion THE ORGANS CONCERNED IN DIGESTION 331 Fig. 293.-Ducts of the pancreas. Part of the front wall of the duodenum is cut away. (Testut.) Fig. 294.-Cavity of the caecum, its front wall having been cut away. The ileocaecal valve and the opening of the appendix are shown. (Testut.) Fig. 295.-The caecum, dorso-mesial view, showing the ileum-side of the ileocaecal valve, and the beginning of the three muscular ribbons. (Testut.) 332 THE DIGESTIVE SYSTEM "insulin," affects the digestion of sugars, so they are retained in the blood and the condition of glycosuria results. Absorption. -The combination of forces acting on the food in the intestine, chemical, thermal and mechanical, reduce it to a condition in which it will pass through the walls of the capillaries and the Fig. 296.-Sigmoid colon and rectum, front view. The broken lines indicate the situation of the concealed part of the sigmoid .colon. The small intestine is drawn away, and the anus is turned forward. (Testut.) lymph radicles into the general circulation. Throughout the 20 feet of small intestine this absorption takes place until the material reaches the beginning of the large intestine. Little then remains except the waste of the food, that is, the parts of the food that cannot yield nourishment, and water. This arrives at the beginning of the large intestine about twelve hours after it was first ingested. 333 THE ORGANS CONCERNED IN DIGESTION The Large Intestine.-This consists of the colon and the rectum. The colon is divided into the caecum, the ascending colon, the trans- verse colon, the descending colon and the sigmoid flexure. The caecum is the blind pouch at the beginning of the colon, in the lower right side of the abdomen. From it a small tube passes from the back part, called the "vermiform appendix" (Figs. 294 and 295). Pass- ing up the right side of the abdomen, as high as the liver is the ascending colon. As the transverse colon it goes across the abdomen from right to left and becomes the descending colon at the spleen. It passes downward on the left side in the iliac fossa to the level of the crest where it becomes the sigmoid colon or flexure. The sigmoid colon is "S" shaped and is the final receptacle of the waste material. Here it remains as feces, until its presence produces a desire for its evacuation. The feces then pass into the rectum, from which it is expelled by the combined peristaltic move- ment and the pressure exerted by the abdominal muscles and the diaphragm. The outlet of the rectum is the anus. This is closed by two sphincter muscles, the internal of which is not under the control of the will and the external sphincter which is kept closed by the will or opened at will. (Fig. 296.) About twelve hours are required to expel the waste products after it enters the colonf or twenty-four hours after eating, the waste of the food is expelled. QUESTIONS. What relation exists between the composition of the body and the composi- tion of the common foods? Name the processes in converting food into a part of the body in the order of occurrence. What chemical agents are involved in digestion? What mechanical agents are involved in digestion? Name the enzymes acting on food in the stomach, in the mouth, in the intes- tine. What are the uses of teeth? Name and locate the salivary glands. What are the functions of the tonsils? What are the successive steps in the digestion of proteins? What is glycogen? Where does it originate? Describe "villi." Of what use are they? What are "lacteals"? Describe a lobule of the liver. What secretion is produced in the "islands of Langerhans"? Its use? What are the parts of the large intestine, and their uses? CHAPTER XI. DIETETICS, NUTRITION AND ANIMAL HEAT. CLASSES OF FOOD AND HOW DIGESTED. Having considered the apparatus by which food is digested it remains to describe the kinds of food according to their chemical composition. Very few foods are purely and strictly in one clas's, but most of them are a combination of carbohydrates, protein and fats, in varying proportions. A glance at the table following will show the percentages of the three classes in some of the commoner articles of diet. The meats have much water, considerable protein, some fat, but little carbo- hydrate. They are classed as protein food. Certain vegetables as beans and peas contain little water, as much protein as meat and considerable starch. They are the vegetable proteins. The various so-called carbohydrate foods contain small quanti- ties of protein in many cases, but are mainly starches and sugars. The starches are found in cereals, potatoes, some fruits and legumes. The sugars include cane sugar, maple, beet, grape, malt and milk sugars as well as that found in meat. Carbohydrates are the least expensive of the various kinds of food and constitute the larger bulk of articles eaten. They are easily oxidized and converted into heat and muscle energy, and into fatty tissue, when taken in excess of the body needs. The digestion of starches occurs in the mouth and small intestine in the presence of the amylolytic enzymes, ptyalin, amylase and pancreatic diastase. The digestion of sugars occurs in the small intestine, in the pres- ence of the sugar-splitting enzymes. Carbohydrates enter the blood as dextrose. Its oxidation results in the production of heat, kinetic energy, II2O and CO2. Fats are either animal or vegetable. The principal forms, accord- ing to their firmness are stearin, palmatin, margarin and olein. They are found in most of the animal foods, in the dairy products and in nuts. Various vegetable oils are derived from the seeds of cotton, from corn, etc. They form a powerful fuel food, giving heat and energy, but are rather difficult to digest and oxidize. The outside envelope of fats is removed in the stomach by the gastric juice, but their digestion takes place in the small intestine by means of bile and steapsin. 334 CLASSES OF FOOD AND HOW DIGESTED 335 AVERAGE CHEMICAL COMPOSITION OF FOODS.1 Food materials. Water, per cent. Protein, per cent. Fat, per cent. Carbo- hydrates, per cent. Ash, per cent. Fuel value calories, per •pound. Beef: Sirloin steak . 61.9 18.9 18.5 1.0 1130 Round steak . 67.8 20.9 18.6 1.1 835 Veal, leg .... 71.7 20.7 6.7 1.1 670 Lamb, leg 58.6 18.6 22.6 1.9 1300 Chops broiled 47.6 21.7 29.9 1.3 1665 Mutton: Roast leg . 50.9 25.9 22.6 1.2 1420 Pork, loin 66.5 18.9 13.0 1.0 900 Smoked ham . 39.8 16.5 38.8 4.7 1945 Chicken .... 70.3 21.9 7.4 1.1 835 Fish: Cod .... 82.6 16.5 0.4 1.2 325 Salmon 64.6 22.0 12.8 1.4 950 Eggs 73.7 13.4 10.5 1.0 720 Butter .... 11.0 1.0 85.0 3.0 3605 Buttermilk . 91.0 3.0 0.5 4.8 0.7 165 Cheese: American . 31.6 28.8 35.9 3.5 2055 Full cream 34.2 25.9 33.7 2.4 3.8 1959 Cream .... 74.0 2.5 18.5 4.5 0.5 910 Whole milk . 87.0 3.3 4.0 5.0 0.7 325 Skimmed milk . 90.5 3.4 0.3 5.1 0.7 170 Cracked wheat . 10.1 11.1 1.7 75.5 1.6 1685 Macaroni 10.3 13.4 0.9 74.1 1.3 1665 Oatmeal .... 7.3 16.1 7.2 67.5 1.9 1860 Rice 12.3 8.0 0.3 79.0 0.4 1630 Flour: Fine white 13.8 7.9 ' 1.4 76.0 0.5 1625 Entire wheat . 11.4 13.8 1.9 71.9 1.0 1675 Bread: White .... 35.3 9.2 1.3 53.1 1.1 1215 Entire wheat . 38.4 9.7 0.9 40.7 1.3 1140 Sugar, fine white 100.0 1860 Vegetables: Green butter beans 58.9 9.4 0.6 29.1 2.0 740 Fresh carrots . 88.2 1.1 0.4 9.3 1.0 210 Green corn 75.4 0.8 1.1 19.7 0.7 470 Green peas 74.6 7.0 0.5 16.9 1.0 465 Boiled potatoes 75.5 2.5 0.1 18.4 1.0 385 Fruits: Apples .... 84.6 0.4 0.5 14.2 0.3 290 Bananas 75.3 1.3 0.6 22.0 0.8 460 Grapes 58.0 1.0 1.2 14.4 0.4 335 Nuts: Almonds . 4.8 21.0 54.9 17.3 2.0 3030 Chestnuts . 45.0 6.2 5.4 42.1 1.3 1125 Peanuts 9.2 25.8 38.6 24.4 2.0 2560 Walnuts 2.5 18.4 64.4 13.0 1.7 3300 Chocolate . 5.9 12.9 48.7 30.3 2.2 2860 Cocoa .... 4.6 21.6 18.9 37.7 7.2 2320 1 Abstracted from "Food Values," by Edwin A. Locke. 336 DIETETICS, NUTRITION AND ANIMAL HEAT Proteins are either animal or vegetable and are found in many forms. Among them are casein in milk and cheese; albumen in the white of egg; vitellin in the yolk of egg; myosin and syntonin in meat; gluten in flour; legumen in peas and beans, and the protein in nuts. Proteins are used in the body for repairing and building-up the cells, as they are stable in their composition. They are the only foods that may be said to be absolutely essential to life, as no repair can take place without them. They may serve as fuel, though they are rather expensive for that purpose, and in addition, put a strain upon the excretory organs. Among the common foods that are predominently protein are: Lean meat, milk, eggs, cheese, fish, wheat, oatmeal, peas, beans and peanuts. The animal proteins are more easily digested than those derived from vegetable sources, and contain less waste. The digestion of proteins occurs in the stomach and the small intestine in the presence of the proteolytic enzymes, pepsin, rennin, trypsin and erepsin. The vegetable foods are usually encased in an envelope of cellu- lose. This is a carbohydrate, but the human digestive tract is unable to break it down. It serves as "roughage" in the intestinal tract, giving bulk to the waste of the food. REQUISITES OF A DIET. It is important to consider what quantity and proportion of the various classes of food are essential to health. In the study of this problem, stated portions of the three principal food elements were burned to determine their value as fuel. The unit of measurement is the calorie, that is, the amount of heat necessary to raise 1 kilo- gram of water 1° C. in temperature. This investigation fixed the fuel value of carbohydrates and proteins at 4.1 calories per gram, and that of fat at 9.3 calories per gram. The analysis of the excreta, the products of perspiration and respiration, shows the amount of carbon and nitrogen, plus the water that is excreted in a given time. This shows the amount of tissue that has broken down by oxidation. As the proportion of the elements in food products is known, it is evident how much food has been consumed and how much must be taken to replace it. Various investigators have examined these relations, and arrived at various results. The principal variant is as to the amount of nitrogen needed to maintain nitrogen equilibrium. By this is meant that the intake of nitrogen equals the outgo. This seems to vary according to the amount ingested. If much nitrogen is taken in much is eliminated. If little nitrogen is taken in, little is eliminated, so that apparently, nitrogenous equilibrium may be maintained 337 METABOLISM with different amounts of nitrogen food. The quantity estimated for an average man doing a moderate amount of work, runs from 75 to 120 gm. of protein a day. With the maximum of 120 gm., go 90 gm. of fat, and 320 gm. of carbohydrates. In estimating the amount of food needed, it is customary to allow 40 calories of food for each kilogram of weight in men, and 30 calories for women. A man weighing 180 pounds would have 3200 calories a day, and a woman of 120 pounds would have 1600 calo- ries by this estimate. This assumes much less muscular activity for women than for men. A rough estimate for the proportionate amounts of food would be 1 part of protein for every 4 parts of fats and carbohydrates combined. Besides the elements of water, O,CHON,CH2O, fats and salts, required by the body certain mate- rials called "vitamines" are needed. Little is known of these, but it is definitely established that they must be supplied to the body or inanition results. The vitamines, "fat-soluble A, and water-soluble B" have been found to have a powerful effect upon the nutrition. Fat-soluble A, is found in butter, but not in lard. Water-soluble B is found in the outer parts of cereals, but is lost in the refining process, as in polish- ing rice. Animal Heat.-The food we eat does more than provide for growth and repair, as it furnishes the means by which heat, motion and thought are produced. Foods possess what is called "potential energy," measured by calories, but the liberated energy may be in the form of heat, kinetic energy or secretion. The different forms of energy are interconvertible as seen above. All oxidative processes are accompanied by the development of heat, so the work of the cells results in heat or its equivalent. Only about one-fifth of the energy developed is in the form of mechanical energy or motion, so only one-fifth of the food taken results in muscular work. The rest of it goes to heat. The force developed in this way is measured in terms of "gram- meters." A grammeter is the amount of energy needed to raise 1 kilogram of weight a distance of 1 meter. Foster calls 150,000 grammeters a good day's work. This is roughly equivalent to a man weighing 180 pounds climbing a mountain 1 mile high in a day. METABOLISM. The process in the cell by which food products are appropriated, their stored up energy utilized and the waste discarded, is called metabolism. The building-up part is anabolism, while the breaking- down and liberating energy is katabolism. When the two are equal, the weight, size and strength of an individual remains the same. When anabolism exceeds katabolism, the size, weight or strength 338 DIETETICS, NUTRITION AND ANIMAL HEAT increases. When katabolism exceeds anabolism, the size, weight or strength decrease, and the storage tissues are called upon. If this continues to starvation, the glycogen in the liver and muscles is first used, then the fats, and finally the protein in the framework, until nothing is left to furnish energy. The vigor with which metabolism is carried on measures the speed of living. A considerable degree of vigor is necessary to health. Various conditions influence metabolism. In hyperthyroidism, the process is much increased, with the reverse in a deficiency of the thyroid secretion. Exercise increases both anabolism and kata- bolism with consequent increase in the elimination of CO2 and H2O. The nitrogen eliminated is also increased, but not markedly unless the carbonaceous food is insufficient to provide for the addi- tional oxidation so that proteins have to be utilized to provide fuel. Then, the output of urea is increased. During sleep the amount of nitrogen waste is about the same as when awake, but the CO2 output is less. Low temperature increases the output of CO2, but not of urea, though it is claimed, no increase occurs unless shivering takes place. Shivering makes for increased muscular work, which increases oxidation. Body Temperature.-If one "takes his temperature" with a clinical thermometer, he finds it to be essentially the same, morning, noon and night; whether the out-door temperature is 20° below zero, or 115° in the shade. The body temperature in man is 98.6° F. or 37° C., and this record persists in health regardless of the surround- ing conditions. There is some wonderful mechanism to insure this, some means of regulating the body response to its environment. Man is called a "warm-blooded" animal as distinguished from the frogs, fish and reptiles that are "cold blooded." These latter change their temperature with their surroundings, but man main- tains a relatively high temperature regardless of that surrounding him. It has been seen that the potential energy of foods becomes either heat or kinetic energy when oxidized in the body cell. According to the activity therein, more or less heat is secreted or thrown off from the glands and muscles. By joint friction, respiration and cardiac activity, additional heat is produced. The highest temperature in the body is in the blood of the portal vein, because of the great glandular activity of the liver. While, the temperature of the body is always essentially the same, there is a small variation of a degree or so, in different parts of the body, at different times of day and with different external tempera- tures. The rectal is a degree higher than the temperature in the mouth; that in the mouth is higher than in the axilla; the evening shows a higher temperature than the early morning; a surface METABOLISM 339 exposed to the cold has a lower temperature than one that is pro- tected. Heat production is called thermogenesis; heat loss is thermolysis: heat regulation is thermotaxis. By thermotaxis, thermogenesis is balanced by thermolysis, so the body remains at the normal tem- perature, and neither force runs wild. In fevers, either thermogenesis may be increased or thermolysis diminished, so the temperature rises. Muscular and glandular activity in making heat are governed by centers in the spinal cord. It is thought these centers maintain a fairly constant production of heat, but the higher centers in the brain may incite them to greater or less activity reflexly. Heat is lost by various means. About 85 per cent is lost by radiation and evaporation from the skin. Some 12 per cent is lost in the lungs by warming the inspired air and evaporation. A small amount is discharged in the urine and feces. Contact with colder objects abstracts heat from the body by conduction. Heat is lost more rapidly when the body is unclothed, as then the layer of dead air between skin and clothing is lacking. Cold moist air and cold water contact lowers the temperature. A short cold plunge at first chills the body, driving the blood from the surface capillaries, but this is shortly followed by a reaction through increased heat production reflexly. Heat is lost when the internal temperature is raised and the external temperature is lowered. Its loss is greater in small bodies than in large ones, because the surface is relatively larger in small animals. Infants need more clothing for this reason than adults and larger children. As women have more subcutaneous fat, and fat is a poor conductor of heat, they can keep warm with less cloth- ing than can men. The greatest factor in equalizing heat production and heat loss is the blood. If a part is cold, more blood sent to it will increase its warmth. If the body surface is exposed to cold, as at 60° or less, the arterioles of the skin contract and the blood goes to the interior regions, where it will not be cooled. Shivering occurs, which by muscular activity promotes heat production. Between 60° and 70°, there is more or less blood in the skin, with the normal distribution between skin and internal organs at 66° to 68°. From 70° to 90°, more blood comes to the skin, the sweat glands become active and perspiration is induced with resulting evaporation which cools the surface. The effect of evaporation may be observed by placing a few drops of ether or gasoline on the skin and noting the chilling of the surface as it evaporates. Nature goes to much trouble to ensure the regulation of the body temperature by automatic nerve centers which increase heat pro- duction when the surroundings of the body would injuriously lower 340 DIETETICS, NUTRITION AND ANIMAL HEAT the temperature, and inducing perspiration and evaporation when the outside temperature becomes higher and liable to interfere with health. It is thus seen how important the function of thermo- taxis is in the economy of the body. QUESTIONS. Define "calories." Define "vitamines." Define metabolism. What quantity and proportions of the various classes of food are necessary in an average diet? If much muscular work is done, which food element should be increased over the amount needed by a person engaged in a sedentary occupation? What is "nitrogen equilibrium"? How is the heat of the body maintained when the outdoor temperature is zero? How is the body kept at a normal temperature when an outdoor thermometer reads 110° F.? CHAPTER XII. THE ORGANS OF EXCRETION AND ELIMINATION. The metabolic processes of the body which include building-up and breaking-down produce a large amount of waste. These wastes are distinguished from the waste of the food which is thrown off through the rectum, having never really entered the body, by the fact that they are in the blood stream, and must be eliminated through the mediation of the microscopical tissues. The CO2 is largely taken from the blood in the lungs, but the nitrogenous wastes, those produced by the breaking-down of pro- teins, are still to be disposed of. Incidentally, this group of waste products, and there are many, is capable of doing much harm to the organism, if retained. The principal organs concerned in this work are the liver, kidneys and skin. The work done by the liver in forming urea has already been considered. This urea is thrown into the blood, and circulates through the body, but at each heart beat, a certain amount of blood goes to the kidneys, and there the further elaboration and elimination take place, with the subsequent ejection of the waste as urine. THE KIDNEYS. These two compound tubular glands, brownish in color, oval in shape, with a resemblance to a bean, are located about the level of the waist, or in the lumbar region, but not in front of the sacrum. They are behind the peritoneum, surrounded by a mass of fat and loose areolar tissue, which with the renal artery, vein and nerve help to prevent their downward displacement. The fascia covering the kidney is connected with the fascia of the quadratus lumborum and psoas magnus muscles, and with these to the aorta. The pres- sure of surrounding organs is another factor in holding the kidneys in place. The upper border is on a level with the upper border of the twelfth thoracic vertebra, while the lower border is level with the third lumbar vertebra. The right kidney is a little lower and wider than the left. They are about 4| inches long, 2 inches wide and 1| inches thick. The weight varies from 4| to 6 ounces. Covering the kidney is a fibrous capsule which continues from the outer surface to the pelvis, lining it as well as the infundibula and the calyces. On the inner and forward part is a depression 341 342 THE ORGANS OF EXCRETION AND ELIMINATION called the hilum, from which arise the ureters, and through which pass the renal artery, vein and nerve. (Fig. 297.) On cutting the kidney lengthwise, it is found to be of a dark red color, with pyramidal spaces of lighter red. (Fig. 298.) The outer border is the cortex or medullary portion with the pyramidal portion toward the center. The latter opens into a cavity, called the pelvis of the kidney, from which also emerge the ureters or excretory ducts of the organ. Three short canals from the pelvis go toward the upper, middle and lower parts of the kidney. These are infundibula. Each divides into several smaller canals called calyces, which receive the apices of the pyramids. Fig. 297.-Right kidney, ventral aspect. (Testut.) The cortical layer, about y inch thick is of a reddish granular structure. It contains the essential, secreting portion of the kidneys, the glomeruli, with the convoluted tubules, bloodvessels and lym- phatics in areolar tissue. The Glomeruli.-These Malpighian bodies or corpuscles or tufts, are from to of an inch in diameter. They consist of a tuft or ball of capillaries from the renal artery, surrounded by the beginning of a renal tubule or capsule, The blood in this tuft, partly by osmosis, partly by cell activity, gives up water and salts which flow into the renal or uriniferous tubule. The capillary on leaving the tuft, becomes a radicle of the renal vein, and forms a network around 343 THE KIDNEYS the first part of the renal tubule. So two networks are formed, the first arterial, the second venous. Uriniferous Tubules.-These are small canals, lined with epithelial cells, secreting cells, which are supposed to take out of the blood the urea, and other waste materials, which are then washed along by the water that entered the beginning of the tubule from the first tuft. This forms the liquid, urine. The uriniferous tubules, immediately after leaving the glomeruli, become intricately convoluted, finally ending in a straight tubule which carries the urine through the pyramids to the calyces. These tubes are from 2"ro °f an inch in diameter. Fig. 298.-Vertical section of kidney, showing the secreting portion, the vessels and the beginnings of the ureter. (Testut.) From the blood the route of the urine is, through the glomeruli, the convoluted tubules, the straight tubules, the calyces, the infun- dibula, to the pelvis of the kidney. Thence through the ureters to the urinary bladder and out through the urethra. The Urine.-Urine is a fluid of light yellow color, acid reaction, specific gravity of 1020, and amounting in twenty-four hours to 344 THE ORGANS OF EXCRETION AND ELIMINATION 1500 cc. Among its constituents are: Urea, uric acid, chlorine, phos- phoric acid, sulphuric acid, creatinin, hippuric acid, oxalic acid, several nitrogenous acids, fatty acids, dissolved nitrogen and carbon dioxide, pigments, as urochrome and urobilin. Under pathological conditions, sugar, albumin, bile, hemoglobin, acetone and other substances may be present. The composition of urine varies according to different conditions of nutrition, exercise, sleep, age, sex, diet, respiratory activity, con- dition of skin and emotions. The principal ingredient is urea, which is found in the blood at all times. A certain percentage is always present, and if the kidneys function properly, all in excess of this normal amount is removed. The presence of urea in the blood seems to be the stimulus which excites the activity of the epithelial secreting cells. The greater the amount of blood with its contained urea that passes through the kidney, the greater the activity of that organ. The amount of blood that passes through is influenced by several factors. 1. External temperature. Cold sends the blood from the skin to the interior organs, while heat reverses the process. 2. By the amount of water ingested. The more water, the more urine. 3. By the amount of protein food. (An excess of protein beyond the needs for repair or building must be eliminated.) 4. By nervous excitement. This increases the amount of urine, but lowers the percentage of solids. 5. By muscular activity. The greater the tissue metabolism, the more urea is formed and eliminated. After the urine collects in the pelvis of the kidney it passes into the ureter, a tube about 18 inches long which goes to the urinary bladder. It penetrates the bladder obliquely, so if the bladder becomes distended the opening from the ureter is automatically closed, and regurgitation to the kidney prevented. As the middle coat of the ureter is muscular, a peristaltic wave carries the urine along, regardless of the position in which the body is placed. THE BLADDER. This is a reservoir for urine, where it is retained until it is con- venient to expel it. It is ovoid in shape, holds about a pint, and is located in the front part of the pelvic cavity. There are three coats, the outer of peritoneum, the middle of plain muscle fibers, and the inner of mucous membrane. The muscular coat is in three layers, with the fibers running in various directions. When it contracts the contents of the bladder are compressed in all directions. THE SKIN 345 The outlet of the bladder is embraced by a thick band of unstriped muscle tissue, the sphincter vesicce. This is usually in tonic con- traction, so preventing the involuntary escape of urine. When the bladder has become moderately full, the desire to expel its contents arises. The act of expelling is micturition, and involves the relaxation of the sphincter, the contraction of the muscular wall of the bladder, aided by the contraction of the abdominal wall. A slight contraction of the abdominal wall compresses the bladder, and the relaxation of the sphincter allows the urine to pass out. The zirethra is a short tube that leads outward from the bladder. THE SKIN. The skin or integument is the external covering of the body, vary- ing in color, texture and thickness. According to the amount of pigment, the color varies from milk- white to black, mahogany, yellow or brown. It varies in texture from a satiny smoothness to a coarse horny roughness. In thickness, it varies from -j- to | of an inch. It has furrows everywhere, which differ in character in different individuals, so the markings of the thumb, for instance, serve for identification. The structure of the skin is in two parts, the corium or true skin, or cutis vera, and the epidermis, scarf skin, which is external to the former. The corium is the active part of the skin, and is very complex. External to and connected with the superficial fascia is a network of areolar tissue, which allows the skin to move freely on the under- lying parts, and which serves as a bed for numerous organs. In this bed are the branchings of the arteries, veins and lymphatics that supply these parts and drain them. An abundant blood supply is evidenced by the fact that it is impossible to pierce the skin any- where without drawing blood. Scattered through the areolar tissue is its specialized form, adipose, as masses of fat, in varying degree, but always present. On the summits of the furrows are elevations called papillae (Fig. 299 and 300), and in the papillae are the end organs of the sense of touch, or Pacinian corpuscles (tactile corpuscles). They are thickly scattered on the skin, with very few areas without them. The endings of the sensory nerves vary in structure, and it is possible there are different ones for each sensation of heat, cold, pressure and pain. The tactile corpuscles are laminated like an onion, with from forty to sixty coats. The nerve fiber penetrates to the middle of this bulb, and finally ends in bulb-like processes. Fig. 300 shows the capillary loops in the papillae from a network 346 THE ORGANS OF EXCRETION AND ELIMINATION Fig. 299.-Vertical section of the skin. (Testut.) Fig. 300.-Papillae of the skin, showing the arrangement of the vessels and nerves. (Testut.) THE SKIN 347 in the cutis vera. Branches go to the fat, sweat and sebaceous glands. Sweat Glands.-The sweat glands are true excretory organs in the skin, to the number of 2,500,000, as estimated. They are tubular glands, coiled up at the inner end to provide greater secreting sur- face, and opening on the surface of the skin, as the pores. The coiled tube is lined with columnar epithelial cells, which take from the blood, water and various salts, sodium chloride largely, and some urea and uric acid, etc. The sweat is more or less profuse according to circumstances, but an average amount is over 2 quarts in twenty-four hours. It is salty in taste, of acid reaction and characteristic odor. By the secretion of visible perspiration and its evaporation, the surface of the body is cooled, and its temperature lowered. This occurs when the external temperature is 70° F. or more, or when the skin temperature is increased by muscular exercise. An occasional person has been found in whom the sweat glands were lacking, necessitating the use of external applications of water when the body temperature threatened to rise unduly. Secretory nerves from the sympathetic rami communicantes are distributed to these glands. The control seems to be automatic and in the medulla. Except for a few areas the whole skin is studded with hairs, vary- ing from a fine down (lanugo) to the stiff hairs of the eyelashes and beard. They vary much in length, thickness and coloring. Straight hair is cylindrical on cross-section, while curly hair has flat places on the curves. A hair consists of a shaft and the root or bulb. The bulb of the hair is whiter and softer than the shaft, and is lodged in an involution of the epidermis, called a follicle. The bulb con- tains various epithelial cells some of which contain pigment, which gives the color to it. (Fig. 299.) The structure of the follicle is rather elaborate, and the shaft of the hair only less so. The shaft consists of a central pith or medulla, a fibrous covering, and an external cuticle of imbricated scales. In the fibrous portion between the cells, are pigment granules in dark hair, or air spaces in white hair. Passing between the surface of the corium and the follicle are small muscles which by their contraction erect the hair. The brist- ling of hairs on the back of a dog's neck when he is angry shows their action more vividly than is possible in human beings. Sebaceous Glands.-Opening into the hair follicles are sebaceous glands, compound racemose in form which secrete oil, serving to prevent dryness of the hair and skin. These glands are also in various other places where little hair is found, as on the nose and eyelids (Meibomian glands). 348 THE ORGANS OF EXCRETION AND ELIMINATION Nails.-Modifications of the epidermis, or appendages of the skin are the nails. The body of the nail is translucent, showing the blood beneath, except at the upper end where a half-moon shaped area, the lunula is more opaque. The free edge of the nail overhangs the end of the toe or finger. The root of the nail is imbedded in a groove of the skin, while the nail-bed holds the nail closely adherent. The proximal part of the bed is the matrix, at which growth takes place, requiring some three months for a complete new nail to grow to the free edge. Epidermis.-The second part of the skin is the epidermis or scarf skin, or cuticle. Two strata, the Malpighian layer and the horny layer stratum corneum, arise from a single layer of columnar cells resting on the corium. The Malpighian layer consists of some four layers, the layer of parent cells above mentioned, then polyhedral prickle cells, with pigment, overlaid by granular cells, and a series of transparent cells, called the "stratum lucidum." These are all nucleated cells, and the upper layers become merged with those of the horny layer which lose their nuclei and become scale-like at the surface and are shed. The bed of the nail is a part of the Malpighian layer. Functions of the Skin.-Some of these have been considered, chief of which is the regulation of the heat of the body; the prolongation of the brain to the surface by the sensory nerves, and the excretion of waste products. Through the sweat glands the skin can throw off much of the nitrogenous waste of the body, serving vicariously for the kidneys when the latter are unable to function. It is a matter of common knowledge that when the body perspires freely, the secretion of urine is lessened in amount, and conversely, when the surface is chilled, so perspiration is checked, the amount of urine is increased. The other uses are more mechanical, as the protection of under- lying parts, preventing the escape of fluids, as blood and lymph, and preserving the contour of the body. QUESTIONS. What is urea? What is urine? Locate the kidneys. What is their function? How does the kidney function compare in importance with that of the stomach? What are the functions of the skin? • Describe the "cutis vera." Where are Pacinian corpuscles found? CHAPTER XIII. THE DUCTLESS GLANDS. Reference has been made to internal secretions or those which are made by glands and pass out into the blood stream, as compared w'ith those that are carried off through a duct, or the external secre- tions. It has been relatively easy to study the latter, experiment with them in laboratories, and determine their function with a fair degree of probable accuracy. The study of internal secretions has been attended with much difficulty, and is still far from being complete. By removal of a gland it has usually been found that its secretion was essential to life. If only partially removed, the animals subjected to the test, showed the necessity for the secretion to influence growth, nutrition and development, mental and physical. Another method of experiment has been the injection of the secre- tion into the circulation of healthy animals and noting the effect. Further light came from feeding the glands to animals in whom the same or another gland had been removed, and finding the apparent effects. The principal ductless glands are the spleen, thyroid, para- thyroids, thymus, adrenal, pituitary, pineal and gonads. The liver and pancreas also have internal secretions which have been discussed under those respective headings. THE SPLEEN. The spleen is a large ovoid body, situated in the posterior part of the abdomen, behind the stomach. It varies in size, in health, but is usually about 5 inches in length, 3 inches wide and 1 inch thick. It weighs about 5 ounces, is of a purplish-red color, friable and soft in consistency. The blood supply of the spleen is very abundant, showing that its function is important, yet its removal has been followed by no permanent bad results. The venous blood from the spleen enters the portal vein, goes through the liver and thence to the vena cava. In this venous blood are many leukocytes, but investigators have found out really little about the function of the spleen. It seems to have some relation to the red corpuscles of the blood, and their hemoglobin, possibly destroying the corpuscles and transforming the hemoglobin. Removal of the spleen is followed 349 350 THE DUCTLESS GLANDS by an anemic condition which lasts but for a short time, with a return to the normal number of corpuscles after some months. Increased amounts of iron are said to be excreted, with a diminu- tion in the amount of bile pigment. After a meal the spleen expands for four or five hours, then returns to its normal size. The circulation of the spleen is supposed to be maintained by a local arrangement which makes it independent of variations of general blood-pressure. During fetal life and soon after birth the spleen forms new red corpuscles, but this is not known to continue into adult life. The organ is larger in childhood and gets smaller after puberty. It has been suggested it may be concerned in the production of uric acid. The spleen may become much enlarged and hardened during malaria. It is also credited with influencing the psychic life in the way of depression and irritability. The structure resembles in some respect that of lymph nodes, and as a whole rather like an enormous group of nodes. THE ENDOCRINE SYSTEM. The glands that are now to be described are supposed to have a definite inter-relation, and are designated as the "endocrine system." The activity of other organs is influenced by the secretions of these glands, the general name of "hormones" being applied to such secre- tions. Some hormones stimulate, others inhibit activity. The Thyroid.-This is a gland lying on the lower part of the front of the larynx, and upper part of the trachea. (Fig. 301.) It has two lateral lobes connected at the lower part by an isthmus. Each is about 2 inches long, f of an inch thick and | of an inch wide. It is relatively larger in infants than in adults. It weighs about 1 ounce. It is divided into lobules by the prolongation inward of the outer fibrous coat. These in turn are composed of closed vesicles, which are lined with columnar epithelium, secreting a colloid material. Removal of the thyroid produces a state of chronic malnutrition. It has, therefore, a profound influence upon nutrition and develop- ment. Its secretion acts upon the body cells to increase meta- bolism. Normal persons who take thyroid extract have the metabolic function increased with resulting increase in bodily heat and energy, and increased elimination of nitrogen and carbon dioxide. The stimulating effect may be so marked it is well described as a " kinetic urge" or desire for activity. Abnormal growth of the thyroid produces hyperthyroidism, or goiter, or exophthalmic goiter, in which the heart rate is much increased, heat production much augmented, and psychic irritability THE ENDOCRINE SYSTEM 351 marked. If the metabolism of normal persons can be indicated by "40," that of such subjects might be indicated by "75." Where there is atrophy of the gland or failure to develop, the con- dition known as cretinism develops. In this there is less metabolic activity than normal, the growth and brain development are stunted, so a child would be of scarcely higher grade than an idiot. The gland extract administered early enough will start up the process of normal development, both physical and mental. PYRAMID OF THYROID BODY Fig. 301.-The thyroid body and the related bloodvessels. (Testut.) When a large part of the thyroid is removed, in adults, the condition known as myxedema results. This exhibits lowered metab- olism, lessened body heat, increased deposition of fat in the tissues, mental hebetude and lack of activity. The Parathyroids.-These are four round bodies, about | of an inch in diameter, closely associated with the thyroid, whose removal is followed by death from tetanus in a short time. It appears their function has something to do with preventing or neutralizing the accumulation of certain toxic products in the blood whose presence causes spasmodic contractions of muscles. 352 THE DUCTLESS GLANDS The Thymus Gland.-This is situated over the upper part of the sternum. Its function is obscure, though it may be concerned with the process of growth. It is said to keep its size and activity until the age of puberty, and then to undergo a gradual atrophy. It is possible there is some reciprocal connection between its function and the development of the reproductive glands. Adrenal Gland.-The adrenal bodies, or suprarenal capsules are conical shaped glands perched on top of the kidneys and imbedded in fat. Their removal from an animal is followed by its death, preceded by great prostration, muscular weakness and lessening of arterial tone. Injections of the gland substance into the circula- tion of a healthy animal results in slowing the rate of the heart beat, and a rise of blood-pressure. The secretion, epinephrin, seems to have some relation to the regulation of the sugar supply or sugar consumption of the body. Strong emotions of fear or anger increase the amount of adrenal secretion. This may mean that when a person is afraid or angry, the increased epinephrin may so stimulate the tonicity of the skeletal muscles, increase the blood going to the nervous system, and make more glycogen available for the muscles, he will be able to make the natural effort to escape the danger or protect himself by an offensive. The Pituitary Body or Hypophysis.-This gland is found at the base of the brain, in the sella turcica of the sphenoid bone. It has an anterior lobe that is fairly large, and a much smaller posterior lobe. When extracts of the posterior lobe are injected the heart beat is slowed and the blood-pressure raised. Most of the involuntary muscles of the body are stimulated as well as some of the glands. The general metabolism is stimulated, particularly through the increased glycogenolysis, by which the glycogen in the liver is made available for use in the muscles. The secretion of the anterior lobe has some effect upon nutrition,- but just what it is a subject for further investigation. Its removal from an animal results in its death in a few days, but death is pre- ceded by a lowering of temperature, rapid emaciation, diarrhea and unsteady gait. If the pituitary gland becomes overgrown there is an increased growth of the osseous system. Excessive height in young persons, and increase in the size of the facial bones or those of the extremities in adults, follow this hypertrophy of the gland. The Pineal Body or Epiphysis.-This is a very small body which seems to grow to its largest size at about the seventh year, there- after, gradually lessening and becoming fibrous instead of glandular. Its secretion seems to cause a lowering of blood-pressure and a lessening of the rate of development of the reproductive organs. THE ENDOCRINE SYSTEM 353 The ancients credited it with being the seat of the human soul. It is located on the under surface of the brain. The Gonads.-These organs, the testis in the male and the ovary in the female produce a secretion from the so-called "interstitial" cells of Leydig. This is necessary to the development of the second- ary sexual characteristics. There are also close relations between these secretions and those of other glands that influence nutrition. QUESTIONS. What is an "internal secretion"? What is the "endocrine system"? Describe the function of the thyroid gland. What conditions result from a deficiency of its secretion? From an excess? Describe the functions of the adrenal glands. Describe the functions of the gonads. Describe the functions of the spleen. INDEX. A Abdominal aorta, 270, 276 cavity, organs within, 318 regions of, 318, 319 Abduction defined, 109 Abductor hallucis muscle, 183 minimi digiti pedis muscle, 185 pollicis muscle, 161 Absorption, 309 Accessorius ad ilio-costalem muscle 188 Acetabulum, 88 Acromion, 75 Adduction defined, 109 Adductor brevis muscle, 169 gracilis muscle, 169 longus muscle, 169 magnus muscle, 165 pectineus muscle, 169 pollicis muscle, 161 Adenoid vegetations, 293 Afferent nerves, 230 Alimentary canal, 311 Alveoli, 296 Amino-acids, 321 Amoeba, 27 Amphiarthrodial joints, 108 Anabolism, 337 Anatomical neck of humerus, 77 position, 20 Anatomy defined, 17 animal, 20 applied, 20 artistic, 20 descriptive, 20 microscopical, 20 pathological, 20 regional, 20 relational, 20 surgical, 20 systematic, 20 Anconeus, 148 Ankle-joint, movements of, 127 Annular ligament of ankle, 216 of wrist, 215 Anterior crural nerve, 248 interosseous nerve, 243 nares, 257 tibial artery, 271 nerve, 251 Anterior ulnar vein, 281 Anus, 333 Aorta, 270 abdominal, 270, 276 divisions of, 270 thoracic, 270, 276 Aortic valve, 264 Aqueous humor of eye, 254 Arachnoid membrane of brain, 219 of spinal cord, 232 Arch, longitudinal, of foot, 106 palmar, 275 plantar, 272 transverse, of foot, 107 Arterial recoil, 287 tension, 287 Arterioles, 266 Artery, anastomosing branches 265 anatomy of, 264 anterior tibial, 271 aorta, 270 articular branches of, 265 axillary, 275 basilar, 275 brachial, 275 brachio-cephalic, 270 bronchial, 276 cceliac axis, 276 common carotid, 272 iliac, 270 coronary, 270 deep branches of, 265 divisions of, 265 external carotid, 273 iliac, 271 femoral, 271 gastric, 276 hepatic, 276 inferior mesenteric, 276 innominate, 270 intercostal, 276 internal carotid, 273 iliac, 271 mammary, 275 lumbar, 278 nutrient branches of, 265 oesophageal, 276 ovarian, 278 pericardial, 276 phrenic, 278 355 356 INDEX Artery, plantar arch, 272 popliteal, 271 posterior tibial, 271 pulmonary, 270 radial, 275 recurrent branches of, 265 renal, 276 splenic, 276 subclavian, 275 subcostal, 276 superficial branches of, 265 superior intercostal, 275 mesenteric, 276 suprarenal, 276 thyroid axis, 275 ulnar, 275 vertebral, 275 Arthrodia, 109 Articular process of vertebra, 60 Articularis genu muscle, 173 Articulations, 108 ankle, 127 atlas and axis, 112 carpo-metacarpal, 119 hip, 120 knee, 123 lower extremity, 120 medio-tarsal, 130 metacarpo-phalangeal, 119 occipito-atlantal, 112 pelvic, 120 phalangeal, 119, 130 radio-ulnar, 119 scapulo-clavicular, 114 shoulder-joint, 115 sterno-clavicular, 113 sternum and ribs, 112 tarsal, 128 thorax, 112 tibio-fibular, 127 of upper extremity, 113 of vertebral column, 109 articular processes, 110 bodies, 109 laminae, 110 spinous processes, 110 transverse processes, 110 Aspera, linea, 96 Association function of cord, 235 Astragalus, 100 Atlas, 60 Auditory nerve, 255 Augmentation in cord, 236 Auricles of heart, 261 Auricular surface of ilium, 89 of sacrum, 66 Automatic action of cord, 236 Autonomic nervous system, 252 Axillary artery, 275 Axis, 61 Axis-cylinder process, 49 Axone, 49 Azygos veins, 279 ±5 Ball and socket joint, 109 Basement membrane, 38 Basilar artery, 275 Basilic vein, 282 Biceps muscle, 145 flexor cruris muscle, 170 Bicipital tuberosity of radius, 82 Bile, 326, 329 Bladder, gall, 329 urinary, 344 Blood, 51 as a carrier, 290 clotting of, 290 color of, 51 composition of plasma of, 52 distribution of, in body, 51 dust, 52 quantity of, in body, 51, 288 temperature of, in liver, 51 Body, temperature of, 338 of vertebra, 60 Bone and Bones, 34, 54 animal matter in, 35 canaliculi in 35 cancellous, 35 carpal, 88 clavicle, 74 compact, 35 earthy matter in, 35 ethmoid, 57 femur, 93 fibula, 99 frontal, 56 hip, 88 hyoid, 72 ilium, 88 inferior maxillary, 58 ischium, 89 lachrymal, 58 lacunae in, 35 lamellae in, 35 malar, 58 mandible, 58 markings of, 55 metacarpal, 88 metatarsal, 106 mineral matter in, 35 nasal, 58 occipital, 56 os innominatum, 88 palate, 58 parietal, 56 periosteum of, 37 pubic, 92 radius, 81 recent, 35 scapula, 75 shapes of, 54 sphenoid, 57 superior maxillary, 58 tarsal, 100 INDEX 357 Bone and Bones, temporal, 56 thigh, 93 tibia, 97 turbinated, 59 ulna, 81 vomer, 59 Brachial artery, 275 plexus, 241 Brachialis muscle, 145 Brachio-cephalic artery, 270 Brachio-radialis muscle, 145 Brachium, 77 Brain, 219 Bronchi, 295 Bronchial artery, 276 Bronchioles, 296 Brunner's glands, 324 Buccinator muscle, 200 Burdach's column, 236 Bursa acromialis subcutanea, 213 bicipitis cruris, 214 bicipito-radialis, 213 condylii externi, 214 interni, 214 infrapatellaris, 214 malleoli externi subcutanea, 214 interni subcutanea, 214 olecrani subcutanea, 213 poplitei, 214 postcalcanea profunda, 214 prepatellaris subcutanea, 214 pretibialis, 214 sartorii, 214 semimembranosi, 214 subacromialis, 213 suprapatellaris, 214 tibialis interna, 214 trapezii, 213 Bursae, 213 Bursal synovial membrane, 40 C Calcaneum, 100 Calories, 336 Calyces of kidneys, 342 Canaliculi, 35 Capillaries, anatomy of, 266 pulmonary, 269 systemic, 269 Capitellum, 81 Carbohydrates, 307 Carbonate of soda, 326 Cardiac cycle, 286 muscle tissue, 49 orifice, 318 Carpus, 88 Carrier organs of body, 23 Cartilage, hyaline, 34 permanent, 34 temporary, 34 white fibro-, 34 Cartilage, yellow elastic, 34 Cauda equina, 232 Cavity of pelvis, 93 Cell or Cells, 26 aggregation of, 28 assimilation, 309 cardiac muscle, 49 ciliated epithelial, 39 columnar, 38 differentiation of, 27 glandular, 39~ muscle, 45 nerve, 49 pigment, 39 polyhedral, 40 shape of, 29 striated muscle, 45 unstriped muscle, 47 Cellulose, 336 Central canal of cord, 233 fissure, 223 Cerebellum, 220, 226 functions of, 231 Cerebral cortex, 222 fissures, 222 hemispheres, 223 lobes, 223 Cerebrospinal fluid, 220 nerves, 236 Cerebrum, 221 functions of, 229 Cervical plexus, 238 branches of, 238 Cervicales ascendans muscles, 187 Chordae tendineae, 264 Choroid, 254 Chyle, 326 Chyme, 322 Compressor nares, 200 Conditional reflexes, 230 Condyle, external, 80 internal 80 Condyloid joints, 109 Conjunctiva, 255 Contraction, latent period, 46 of muscle, 46 Coordination in spinal cord, 236 Coraco-brachialis muscle, 142 Coracoid process, 75 Cornea, 254 Coronal plane, 20 Coronary artery, 270 Coronoid fossa, 80 Corrugator supercilii muscle, 200 Corpus callosum, 224 Corpuscles, red, 52 white, 52 Cortex, 222 functions of, 229 Cotyloid ligament, 120 Cranial nerves, 237 abducent (6), 238 auditory (8), 238 358 INDEX Cranial nerves, facial (7), 238 glosso-pharyngeal (9), 238 hypoglossal (12), 238 motor-oculi (3) 237 olfactory (1), 237 optic (2), 237 pneumogastric (10), 238 spinal accessory (11), 238 trifacial (5), 238 trochlear (4), 237 vagus (10), 238 reflexes, 230 Crest of ilium, 88 of os pubis, 92 Cretinism, 351 Crossed pyramidal tract, 235 Cross-striped muscle, 45 Crypts of Lieberkuhn, 323 Cuboid, 101 Cuneiform bones, 106 Curves of spine, 67 Cutis vera, 345 Cystic duct, 329 D Decussation of pyramids, 228 Deglutition, 309, 316 Deltoideus muscle, 140 Dendrites, 49 Dentin, 37 Depressor al® nasi muscle, 200 anguli oris muscle, 200 labii inferioris muscle, 200 Diaphragm, 194 Diarthrodial joint, 108 Diastole, 286 Diet, requisites of, 336 Digastricus muscle, 198 Digestion, chemical changes in, 309 organs concerned in, 311 Digestive system, 306 Direct pyramidal tract of cord, 235 Dorsal interossei muscle, 157, 185 Duct, Santorini's, 330 Ductus communis choledochus, 329 Duodenum, 322 Dura of brain, 219 of cord, 232 Dyspnea, 300 E Ear, 256 external, 256 auditory meatus, 256 internal, 256 middle, 256 ossicles of, 256 Efferent nerves, 230 Elbow-joint, ligaments of, 117 movements of, 118 Encephalon, 219 Endocardium, 264 Ensiform cartilage, 67 Enzymes, 309 amylase, 310, 324 amylolytic, 310 coagulating, 310, 324 erepsin, 310, 324 invertase, 310 lactase, 310 lipase, 310 lipolytic, 310 liver glycogenase, 310 maltase, 310 muscle glycogenase, 310 pepsin, 310, 321 proteolytic, 310 ptyalin, 310, 316 rennin, 310, 321 steapsin, 310, 324 sugar splitting, 310 trypsin, 310, 324 Epidermis, 348 Epiglottis, 293 Epinephrin, 352 Epiphysis, 352 Epithelial membrane, 39 Equilibrium, nitrogenous, 336 Erector spin® muscle, 188 Erythrocytes, 52 Esophageal artery, 276 Esophagus, 316 Ethmoid, 57 Eupncea, 300 Eustachian tube, 256 Exchange of O and CO2, 304 Excretion, 40 Expiration, active, 300 passive, 300 Extension defined, 109 Extensor brevis digitorum muscle, 183 pollicis muscle, 160 carpi radialis brevis muscle, 152 longus muscle, 152 ulnaris muscle, 152 communis digitorum muscle, 156 indicis muscle, 156 longus digitorum muscle, 183 pollicis muscle, 161 minimi digiti muscle, 156 ossis metacarpi pollicis muscle, 160 proprius hallucis muscle, 182 External anterior thoracic nerve, 242 carotid artery, 273 iliac artery, 271 jugular vein, 279 plantar nerve, 251 saphenous vein, 283 Eye, 254 F Falciform lobe, 223 Falx cerebelli, 221 INDEX 359 Falx cerebri, 221 Fascia, 214 lata, 215 palmar, 215 plantar, 218 superficial, 215 Fats, 308 Femoral artery, 271 Femur, 93 Fenestra ovalis, 256 Fibrinogen, 290 Fibula, 99 Filum terminale, 232 Fissure, central, 223 longitudinal, 223 parieto-occipital, 223 Rolandic, 223 Sylvian, 223 Fissures of cord, 232 Flexion defined, 109 Flexor accessorius muscle, 181 brevis digitorum muscle, 181 hallucis muscle, 180 minimi digiti muscle, 156 pedis muscle, 182 pollicis muscle, 160 carpi radialis muscle, 150 ulnaris muscle, 150 longus digitorum muscle, 180 hallucis muscle, 180 pollicis muscle, 160 ossis metacarpi minimi digiti mus- cle, 153 pollicis muscle, 158 profundus digitorum muscle, 153 sublimis digitorum muscle, 153 Food purveyors of body, 22 Foods, carbohydrates in, 334 classes of, 334 fats in, 334 mineral salts in, 307 proteins in, 336 vitamines in, 337 • water in, 307 Foot, 100 Fossa, glenoid, of scapula, 75 Framework of body, 22 Frontal bone, 56 lobe, 223 plane, 20 Frontalis muscle, 200 Functions of cord, 235 G Gall-bladder, 329 Ganglia, inferior cervical, 252 middle cervical, 252 prevertebral, 252 sporadic, 253 superior cervical, 252 Ganglion impar, 252 Gastric artery, 276 digestion, 309 juice, 321 Gastrocnemius muscle, 177 Gemellus, inferior and superior mus- cles, 170 General circulation, 270 Genio-hyoid muscle, 198 Ginglymus joints, 109 Girdle, pelvic, 93 shoulder, 73 Gladiolus, 67 Glands, 40 accessory to digestive tract, 326 adrenal, 352 Brunner's, 324 compound, 42 ductless, 349 endocrine, 350 gastric, 321 internal secretion of, 349 parathyroid, 351 parotid, 315 pineal, 352 pituitary, 352 racemose, 42 salivary, 315 sebaceous, 347 solitary, 323 sublingual, ,315 submaxillary, 315 sweat, 347 thymus, 352 thyroid, 350 tubular, 42 Glandular tissue, 39 Glomerulus, 342 Glottis, 295 effect of closing in expiration, 295 in inspiration, 295 Gluteal lines, 89 ridge, 96 Gluteus maximus muscle, 162 medius muscle, 164 minimus muscle, 164 Glycogen, 327 Gonads, 353 Grammeter, 337 Gray matter of cord, 233 nervous tissue, 49 Great sciatic nerve, 251 Gustatory nerve, 257 H Hair, 347 Heart, anatomy of, 261 apex beat of, 287 auricles of, 261 innervation of, 286 steadying output of, 287 valves of, 263 360 INDEX Heart, ventricles of, 261, 262 Hemispheres, cerebral, 223 Hepatic artery, 276 duct, 329 vein, 280 Hilum of kidney, 342 Hip-joint, capsular ligament of, 120 ilio-femoral band of, 120 ligamentum teres of, 120 movements of, 123 "Y" ligament of, 120 I Ileum,322 Iliac crest, lips of, 89 Iliacus muscle, 162 Ilio-costalis muscle, 188 Ilio-hypogastric nerve, 248 Ilio-inguinal nerve, 248 Ilium, 88 Impar, ganglion, 252 Inferior maxillary bone, 58 mesenteric artery, 276 turbinated body, 257 Infraspinatus muscle, 144 Infundibulum, 342 Inguinal canal, 193 Innominate artery, 270 Inscription, tendinous, 44 Inspiration, 300 forced, 300 Insula, 223 Insulin, 332 Intercellular spaces, 51 substance, 28 Intercostal artery, 276 Intercostalis externi muscle, 195 interni muscle, 195 Internal anterior thoracic nerve, 242 carotid artery, 273 cutaneous nerve, 242 iliac artery, 271 jugular vein, 279 mammary artery, 275 plantar nerve, 251 saphenous vein, 283 Interossei dorsalis pedis muscle, 185 plantaris muscle, 185 Interstitial cells of Leydig, 353 Intertrochanteric lines, 96 Intervertebral disks, 109 foramina, 60 Intestinal digestion, 309 juice, 323 Intestine, large, divisions of, 333 small, movements of, 326 Intra-abdominal pressure, 302 Intrapulmonary pressure, 301 Intrathoracic pressure, 301 Iris, 254 Ischium, 89 J Jejunum, 322 Joints, amphiarthrodial, 108 diarthrodial, 108 synarthrodial, 108 Juice canals, 268 K Katabolism, 337 Kidneys, anatomy of, 341 location of, 341 Kinesthetic sense, 260 Kinetic urge, 350 Knee-joint, bursse of, 126 ligaments of, 123, 126 synovial membrane of, 123 L Lachrymal bone, 58 duct, 255 gland, 255 Lacteals, 326 Lacunae, 35 Lamellae, 35 Laminae of vertebrae, 60 Langerhans, islands of, 330 Laryngo-pharynx, 293 Larynx, 293 Latissimus dorsi muscle, 142 Lens, crystalline, 254 Lesser internal cutaneous nerve, 242 Leucocytes, 51 Levator anguli oris muscle, 198 costarem muscle, 195 labii inferioris muscle, 200 superioris alaquae nasi muscle 198 proprius muscle, 198 scapulae muscle, 138 Leydig, interstitial cells of, 353 Ligament, alar, of knee, 126 annular, of ankle, 216 of wrist, 215 capsular, of shoulder, 115 coronary, of knee, 123 cotyloid, 120 crucial, 123 gleno-humeral, 116 ischio-f emoral, 123 mucosa, of knee, 126 orbicular, 119 patellar, 123 plantar, 130 Poupart's, 192 pubo-f emoral, 121 teres, 120 transverse, of knee, 123 Winslow's, 123 Limbic lobe, 223 INDEX 361 Linea alba, 192 Liquid tissues, 51 Liver, lobes of, 326 Lobes, caudatus, 326 cerebral, 223 falciform, 223 frontal, 223 insula, 223 limbic, 223 occipital, 223 parietal, 223 quadratus, 326 Spigelii, 326 temporal, 223 Lobules of liver, 327 Lobulettes, 296 Long saphenous vein, 283 subscapular nerve, 242 Longissimus dorsi muscle, 189 Longus colli muscle, 198 Lymph, 51, 289 nodes, 289 nodules, 323 radicles, 268 spaces, 268 work of, 289 M Malar bone, 58 Malleolus, external, 100 internal, 98 Malpighian corpuscle, 342 Mandible, 58 Manubrium, 67 Masseter muscle, 200 Master organs of the body, 24 Mastication, 309 Median basilic vein, 282 cephalic vein, 281 nerve, 242 vein, 282 Mediastinum, 297 Medio-tarsal joint, 130 Medulla, 220 Membrana tympanum, 256 Membranes, 39 arachnoid, 220, 232 Schneiderian, 258 Meninges of brain, 219 of cord, 232 Mesial, 20 Metabolism, 337 Metacarpal bones, 88 Metatarsal bones, 106 Middle turbinated body, 257 Mind, subconscious, 254 Mineral salts in body, 307 Mitral valve, 264 Motor centers of brain, 230 Mouth, 311 Movements of foot, 161 Movements of leg, 161 of segments of upper extremity, 135 of shoulder, 135 of spinal column, 111 of thigh, 161 of toes, 162 Muscle or Muscles, 132 abductor hallucis, 183 minimi digiti pedis, 185 pollicis, 161 accessorius ad ilio-costalem, 188 adductor brevis, 169 gracilis, 169 longus, 169 magnus, 165 pectineus, 169 pollicis, 161 anconeus, 148 articularis genu, 173 biceps, 145 flexor cruris, 170 brachialis, 145 brachio-radialis, 145 buccinator, 200 cervicales ascendens, 189 complexus, 189 compressor nares, 200 contraction of, 46 coraco-brachialis, 142 corrugator supercilii, 200 deltoideus, 140 depressor alae nasi, 200 anguli oris, 200 labii inferioris, 200 diaphragm, 194 digastricus, 198 direct action of, 134 erector, spina;, 188 of expression, 198 extensor brevis digitorum, 183 pollicis, 160 carpi radialis brevis, 152 longus, 152 ulnaris, 152 communis digitorum, 156 indicis, 156 longus digitorum, 183 pollicis, 161 minimi digiti, 156 ossis metacarpi pollicis, 160 proprius hallucis, 182 of eyeball, 255 flexor accessorius, 181 brevis digitorum, 181 hallucis, 180 minimi digiti, 156 pedis, 182 pollicis, 160 carpi radialis, 150 ulnaris, 150 longus digitorum, 180 hallucis, 180 362 INDEX Muscle or Muscles, flexor longus polli- cis, 160 ossis metacarpi minimi digiti, 153 pollicis, 158 profundus digitorum, 153 sublimis digitorum, 153 frontalis, 200 gastrocnemius, 177 gemelli, 170 genio-hyoid, 198 gluteus maximus, 162 medius, 164 minimus, 164 grouped according to function, 200 iliacus, 167 ilio-costalis, 188 infraspinatus, 144 insertion of, 133 intercostales externi, 195 interni, 195 interossei dorsalis, 157 pedis, 185 palmaris, 157 plantaris, 185 latissimus, 142 levator anguli oris, 198 costarem, 195 labii inferioris, 200 superioris alaeque nasi, 198 proprius, 198 scapulae, 138 as levers, 133 longissimus dorsi, 189 lumbricales, 156, 182 multifidus spinae, 190 mylo-hyoid, 198 naming of, 134 obliquus capitis inferior, 190 superior, 190 externus abdominis, 191 internus abdominis, 193 obturator externus, 169 internus, 169 occipitalis, 200 omo-hyoid, 198 orbicularis oris, 198 palpebrarum, 200 origin of, 133 palmaris longus, 150 pectoralis major, 141 minor, 140 peroneus brevis, 179 longus, 177 tertius, 173 plantaris, 177 platysma, 198 popliteus, 171 pronator quadratus, 148 teres, 148 psoas magnus, 162 pterygoideus externus, 200 Muscle or Muscles, pterygoideus inter- ims, 200 pyramidalis, 191 nasi, 200 pyriformis, 170 quadratus femoris, 170 lumborum, 194 quadriceps extensor cruris, 170 rectus abdominis, 190 capitis anterior major, 198 minor, 198 lateralis, 198 posterior major, 190 minor, 190 femoris, 171 reversed action of, 134 rhomboideus major, 139 minor, 138 risorius, 198 rotatores spinae, 190 sartorius, 170 scalenus anterior, 196 medius, 197 posterior, 197 semimembranosus, 171 semispinalis capitis, 190 cervicis, 190 dorsi, 190 semitendinosus, 171 serratus magnus, 139 posterior inferior, 185 superior, 185 soleus, 177 spinalis dorsi, 188 splenius capitis, 186 cervicis, 186 sterno-hyoid, 198 sterno-mastoideus, 198 sterno-thyroid, 198 stylo-hyoid, 198 subclavius, 140 subcostales, 196 subscapularis, 145 supinator, 148 supraspinatus, 140 temporalis, 200 tensor fascia lata, 163 tarsi, 200 teres major, 143 minor, 145 thyro-hyoid, 198 tibialis anterior, 173 posterior, 173 trachelo-mastoid, 189 transversalis abdominis, 194 cervicis, 189 trapezius, 136 triangularis sterni, 196 triceps, 148 vastus externus (lateralis), 172 intermedius, 173 internus (medialis), 172 zygomaticus major, 198 INDEX 363 Muscle or Muscles, zygomaticus minor 198 Muscular coat of small intestine, 323 of stomach, 320 sense, 260 Musculo-cutaneous nerve, 242, 251 Musculo-spiral nerve, 243 Mucous coat of small intestine, 323 of stomach, 321 membrane, 39 Multifidus spime muscle, 190 Myelon, 231 Mylo-hyoid muscle, 198 Myxoderma, 351 N Nails, 348 matrix of, 348 Nares, posterior, 293 Nasal bones, 58 Naso-pharynx, 293 Neck, surgical, of humerus, 77 Nerve cell, 49 Nerves, afferent, 51 anterior crural, 248 interosseous, 243 tibial, 251 auditory, 255 circumflex, 243 efferent, 51 external anterior thoracic, 242 plantar, 251 great sciatic, 251 gustatory, 257 ilio-hypogastric, 248 • ilio-inguinal, 248 internal anterior thoracic, 242 cutaneous, 242 plantar, 251 lesser internal cutaneous, 242 long subscapular, 242 median, 242 musculo-cutaneous, 242, 251 musculo-spiral, 243 obturator, 249 olfactory, 257 peroneal, 251 popliteal, 251 posterior interosseous, 243 thoracic, 242 tibial, 251 radial, 243 of special sense, 254 splanchnic, 253 suprascapular, 242 of touch, 258 ulnar, 243 vaso-constrictors, 289 vaso-dilators, 289 vaso-motor, 253 Nervous tissue, 49 Neural arch, 60 Neurilemma, 49 Neuron, 49 Nose, 257, 292 Nuchae, ligamentum, 110 O Obliquus capitis inferior muscle, 190 superior muscle, 190 externus abdominis muscle, 191 internus abdominis muscle, 193 Oblongata, 220, 227 Obturator externus muscle, 169 foramen, 89 internus muscle, 169 nerve, 249 Occipital bone, 56 lobe, 223 Occipitalis muscle, 200 Odontoid process of axis, 61 Olfactory nerve, 257 (Esophageal artery, 276 Olecranon, 81 Omentum, 320 Omo-hyoid muscle, 198 Orbicularis oris muscle, 198 palpebrarum muscle, 200 Organs of motion, 23 Oro-pharynx, 293 Os innominatum, 88 pubis, 92 Ossicles of ear, 256 Ovarian artery, 278 P Pacinian corpuscles, 345 Palate bones, 58 Palmar arches, 275 fascia, 215 interossei muscles, 157 Palmaris longus muscle, 150 Pancreas, 329 Pancreatic juice, 324 Parietal bones, 56 lobe, 223 Parieto-occipital fissure, 223 Parotid glands, 315 Patella, 96 Pectoralis major muscle, 141 minor muscle, 140 Pedicles, 60 Pelvic cavity, 93 girdle, 93 Pelvis, 92 contents of, 93 of kidneys, 342 Pepsin, action of, 321 Peptone, 321 Pericardial artery, 276 364 INDEX Pericardium, 261 Periosteum, 37 Peripheral resistance, 287 Peristalsis, 322 Peritoneum, 318 Perivascular spaces, 268 Peroneal nerve, 251 Peroneus brevis muscle, 179 longus muscle, 177 tertius muscle, 173 Phagocytes, 52 Phalanges, 88, 106 Pharynx, 293 Phrenic artery, 278 nerve, 241 Physiology defined, 17 Pia of brain, 219 of cord, 232 Pivot joint, 109 Plain muscle tissue, 47 Plantar arches, 272 fascia, 218 Plantaris muscle, 177 Plasma, 51 Platelets, 52 Platysma muscle, 198 Pleura, parietal, 297 visceral, 297 Plexi of spinal nerves, 238 Pons Varolii, 220, 226 Popliteal artery, 271 nerve, 251 notch, 97 Popliteus muscle, 171 Portal circulation, 280 vein, 280 Posterior interosseous nerve, 243 nares, 257, 293 thoracic nerve, 242 tibial artery, 271 nerve, 251 ulnar vein, 281 Poupart's ligament, 192 Prehension, 309 Pre vertebral ganglia, 252 Primary proteoses, 321 Processes in converting food, 308 Pronator quadratus muscle, 148 teres muscle, 148 Properties of a living body, 25 Proteins, 308 Psoas magnus muscle, 162 Pterygoideus externus muscle, 200 internus muscle, 200 Pyloric orifice, 318 Pyramidal cells of cortex, 231 Pyramidalis muscle, 191 nasi muscle, 200 Pyramids of brain, function of, 231 decussation of, 228 Pyriformis muscle, 170 Pulmonary artery, 270 capacity, 303 ! Pulmonary capillaries, 269 circulation, 270 valve, 264 Pulse, 287 Q Quadratus femoris muscle, 170 lumborum muscle, 194 Quadriceps extensor cruris muscle, 170 R Radial artery, 275 nerve, 243 Vein, 281 Radio-ulnar articulation, 119 Radius, 81 Rami of os pubis, 92 Ramus communicans, 252 of ischium, 89 Ranvier, nodes of, 49 Receptaculum chyli, 284 Reciprocal reception joint, 109 Recoil, arterial, 287 Rectum, 333 Rectus abdominis muscle, 190 capitis anterior major muscle, 198 minor muscle, 198 lateralis muscle, 198 posterior major muscle, 190 minor muscle, 190 femoris muscle, 171 Red corpuscles, 289 work of, 289 Reflex action of cord, 236 arc, 236 Reflexes, 230 conditional, 230 cranial, 230 spinal, 230 unconditional, 230 Relation of autonomic and cerebro- spinal systems, 253 system to body func- tions, 253 of parts of the body, 21 Renal artery, 276 Rennin, action of, 321 Reproductive organs, 25 Residual air, 303 Respiration defined, 292 external, 292 internal, 292 mechanism of, 300 organs concerned in, 292 rate of, 301 ratio to pulse and temperature, 301 relation to abdominal functions, 302 to circulation, 301 INDEX 365 Respiration, rhythm of, 301 sounds of, 301 types of, 301 Respiratory movements, innervation of, 305 Retina, 254 Rhomboid ligament, 114 Rhomboideus major muscle, 139 minor muscle, 138 Ribs, 69 angle of, 70 floating, 69 sternal, 69 tubercle of, 69 vertebral, 69 Risorius muscle, 198 Rolandic fissure, 223 Rotation defined, 109 Rotatores spina? muscles, 190 S Saccule of ear, 257 Sacral plexus, 249 Sacro-iliac synchondrosis, 120 Sacrum, 63 Saddle joints defined, 109 Sagittal plane, 20 Saliva, 316 Sarcoplasm, 45 Sartorius muscle, 170 Scalenus anterior muscle, 196 medius muscle, 197 posterior muscle, 197 Scaphoid, 101 Scapula, 75 Schneiderian membrane, 258 Schwann, white substance of, 49 Sclerotic coat, 254 Sebaceous glands, 347 Secondary proteoses, 321 Secretion, 40 Semicircular canals of ear, 257 Skin, papillae of, 345 Solar plexus, 253 Soleus muscle, 177 Solitary glands, 323 Special centers of cord, 236 Speech centers of brain, 231 Sphenoid, 57 Sphincter vesica* muscle, 345 Spinal column, movements of, 111 cord, 231 association function of, 235 augmentation function of, 236 automatic function of, 236 Burdach's column of, 236 central canal of, 233 commissures of, 233 coordination in, 236 cornu of, 234 Spinal cord, crossed pyramidal tracts of, 235 direct pyramidal tracts of, 235 dura of, 232 fissures of, 232 functions of, 235 gray matter of, 233 meninges of, 232 reflex action of, 236 transference, function of, 236 white matter of, 234 foramen, 60 nerves, 234 plexi of, 238 reflexes, 230 Spinalis dorsi muscle, 188 Spine as a whole, 67 curves of, 67 Spinous processes of ilium, 89 of vertebrae, 60 Splanchnic nerves, 253 Spleen, 349 Splenic artery, 276 Splenius capitis muscle, 186 cervicis muscle, 186 Sporadic ganglia, 253 Sterno-hyoid muscle, 198 Sterno-mastoideus muscle, 198 Sterno-thyroid muscle, 198 Sternum, 67 Stomach, 318 coats of, 320 glands of, 321 greater curvature of, 318 lesser curvature of, 318 Stratum corneum, 348 lucidum, 348 Striated muscle tissue, 44 Stylo-hyoideus muscle, 198 Subclavian artery, 275 Subclavius muscle, 140 Subconscious mind, 254 Subcostal artery, 276 Subcostales muscle, 196 Sublingual glands, 315 Submaxillary glands, 315 Submucous coat of intestine, 323 of stomach, 320, 321 Subscapularis muscle, 145 Succus entericus, 323 Suction pump of circulation, 288 Superficial veins, 281, 283 Superior intercostal artery, 275 maxillary bone, 58 mesenteric artery, 276 turbinated body, 257 Supinator muscle, 148 Supplemental air, 303 Suprarenal artery, 276 capsules, 352 Suprascapular nerve, 242 Supraspinatus muscle, 140 Surgical neck of humerus, 77 366 INDEX Sustentaculum tali, 100 Sweat glands, 347 Sylvian fissure, 223 Sympathetic plexi, 253 Synarthrodial joints, 108 Synchondrosis, sacro-iliac, 120 Synovial fluid, 40 membrane, 40 Syntonin, 321 Systemic capillaries, 266 circulation, 270 Systole, 286 T Tarsal joints, 128 Taste buds, 257 Teeth, 311 Temporal bone, 56 lobe, 223 Temporalis muscle, 200 Tendinous inscription, 44 Tensor fascia lata muscle, 163 tarsi muscle, 200 Tentorium cerebelli, 221 Teres ligament, 93 major muscle, 143 minor muscle, 145 Thermogenesis, 339 Thermolysis, 339 Thermotaxis, 339 Thoracic aorta, 270 Thorax, 71 normal position of, 300 Thrombin, 290 Thyro-hyoid muscle, 198 Thyroid, 350 axis, 275 foramen, 89 Tibia, 97 Tibialis anterior muscle, 173 posterior muscle, 173 Tidal air, 303 Tissue, adenoid, 33 adipose, 32 areolar, 31 cardiac, 49 cartilaginous, 34 connective, 29 dentinal, 37 epithelial, 38 gelatinous, 33 glandular, 39 hyaline cartilage, 34 neuroglia, 33 osseous, 34 plain muscle, 47 striated muscle, 45 white fibro-cartilage, 34 fibrous, 30 yellow elastic, 31 fibro-cartilage, 34 Tongue, 257, 314 Tonsils, 316 Trachea, 295 Trachelo-mastoideus muscle, 189 Transversalis abdominis muscle, 194 cervicis muscle, 189 Trapezius muscle, 136 Triangularis sterni muscle, 196 Triceps muscle, 148 Tricuspid valve, 263 Trochanter, great, 95 lesser, 95 Trochlear surface of humerus, 80 Tuberosities of humerus, 77 Tuberosity, bicipital, 82 of ischium, 89 Turbinated bodies, 58 Tubule, uriniferous, 343 Tympanum, 256 U Ulna, 81 Ulnar artery, 275 nerve, 243 Unconditional reflexes, 230 Unstriated muscle, 47 Urea, 327 Ureters, 342 Urethra, 345 Urine, composition of, 343 Utricle of ear, 257 Uvula, 311 V Vaginal synovial membrane, 40 Valves of heart, 263 of veins, 267 Valvulae conniventes, 323 Vasa vasorum, 265 Vaso-constrictor nerves, 289 Vaso-dilator nerves, 289 Vaso-motor nerves, 253 Vastus externus (lateralis) muscle, 172 intermedius muscle, 173 internus (medialis) muscle, 172 Veins, anatomy of, 267 / anterior ulnar, 281 azygos, 279 basilic, 282 deep, 279 external jugular, 279 saphenous, 283 general arrangement of, 278 hepatic, 280 internal jugular, 279 saphenous, 283 long saphenous, 283 median, 282 basilic, 282 INDEX 367 Veins, median, cephalic, 281 portal, 280 posterior ulnar, 281 radial, 281 short saphenous, 283 superficial, 281, 283 of lower extremity, 283 of upper extremity, 281 systemic, 279 Venous radicles, 266 Venule, 266 Vena cava, inferior, 280 superior, 280 Ventricles of brain, 220 of heart, 261, 262 Vermiform appendix, 333 Vermix, 226 Vertebra, cervical, 60 dorsal, 62 lumbar, 62 prominens, 61 sacral, 63 thoracic, 62 typical, 59 Vertebral artery, 275 body, 60 groove, 71 Villi, 323 Vital capacity, 303 Vitamines in food, 337 Vitreous of eye, 254 Vocal cords, 295 Vomer, 59 W Waste removers of body, 23 Water in body, 307 White corpuscles, 289 work of, 289 fibers of cord, 234 matter of cord, 233 nervous tissue, 49 substance of Schwann, 49 Wrist-joint, ligaments of, 119 movements of, 119 Y Yellow elastic tissue, 31 fibro-cartilage, 34 "Y" ligamentof Bigelow, 121 Z Zygomaticus major muscle, 198 minor muscle, 198