SCIENCE / THE OPPORTUNITY OF ANATOMY? It has been the custom of the past few years for the person whom you have chosen as your presiding officer to give in this hour some comprehensive sur- vey of his own research. But last year you gave a generous allotment of your time to a symposium on the subject in which I am especially interested. At that time I presented the work of my colleagues and myself, it is true in an incomplete form, but as our experiments have since been analyzed and published, I propose, with your permission, to speak on a more general topic. I wish to return to an earlier custom of this society and consider the general subject of teaching. This year marks the end of my career as a teacher: I have taught my last class, I have ceased to be a professional teacher, but remain a professional student; but I have taught for twenty-six years, twenty-three years in a medical school, with such pleasure that I wish to record some of the changes which I have personally lived through in the teaching of anatomy. : The relation of anatomy to medical research is to be my special topic, for both in its position at the beginning of the medical course and in the nature of its subject-matter, anatomy has facilities unsurpassed for turning the minds of students toward research. From the programs of our meetings it is clear that gross anatomy is enlarging its field for research into the domain of anthropology, that neurology is at the present time one of the most brilliant subjects for research, in its almost untrodden field for the corre- lation of structure and function, but it is specifically of histology that I wish to speak this morning, to the thesis, that, in histology, one has a rare opportunity to teach knowledge in its growing zone. That is the definition with which Havelock Ellis in his most fasci- nating new book, “The Dance of Life,” has illumi- nated the relation of science to modern education. When I began the teaching of histology, twenty- three years ago, the. subject was a minor discipline. Histology began with the discovery of the cell, and through its early period it was the isolated cell that dominated its subject-matter; but the cell, isolated by methods of maceration, dilute alcoho! for the epi- thelial cells and weak acids for muscle, had been dead long before it was studied and so we had only gen- eral concepts concerning its form and its relation- 1 Presidential address given before the American Association of Anatomists, 1925. 500 Ships. The microtome was then introduced and we began to study sections. That marked the next phase of the study of histology, namely, the survey of all the organs of the body, in order to learn the general topography of the tissues. It was during this phase of the subject that text-books began to appear. When I began teaching histology we had these two tech- niques. We gave quite simple exercises with isolated eells of each type and about three sections each day to be stained, mounted and studied by the student. We had also frozen sections which we studied mainly for the fibers of the connective tissues. We used them, here and there, to analyze the structure of an organ; for instance, following the work of His, we shook frozen sections of lymph glands in a test tube and speculated on why the follicles fell out and the rest of the framework remained. When I took charge of our ‘course in histology, Dr. Mall gave me only one direction, but advised me to read two books, both of them by English teachers—one, Beale’s “How to Work with the Microscope,”? and the other a little book by Miall on “Thirty Years of Teaching.”? The book of Beale is not a cut-and-dried text-book, with a mere statement of facts, but is the record of a man who had used a microscope with joy to find out things concerning which he was intensely curious. Miall’s book has charm. He was a teacher of biol- ogy in the Yorkshire College and his concept of teach- ing was to help students to love their work. To quote, “Lecturing aims at giving information, teaching aims at discipline. To both teacher and student the way in which a result is got may be far more important than the result itself. . . . When two biologists meet, they tell one another things, but they don’t offer discipline to one another. The professor and an advanced class should be on something like the same terms.” Or again, “The spirit of inquiry is only to be communicated by those who have it, who habitually inquire themselves.” The specific counsel which Dr. Mall gave me was that in outlining any plan of work for students one should never make the directions so specific as to rob the student of his pleasure in discovery and make him mechanically follow a definite procedure. This is the flaw in most of the formally published courses, that they tend to destroy for the student all the pleasure of personal discovery. It is clear that the nature of instructions to be given to students must vary to some extent, indeed perhaps to a marked extent, with the nature of the material to be handled. If material is rare or fragile or involves the use of anesthetized animals, then the directions must be specific, but there 2 Harrison, London, 1868. 3L. C. Miall, professor of biology in the Yorkshire College, Macmillan and Co., London, 1897. SCIENCE [Vou. LXI, No. 1595 are certainly two subjects in the premedical sciences, namely, histology and pathology, where material cay be so unlimited that the student can be given great liberty and be taught wholly ‘in the spirit of finding things out for himself. I have said enough to make it clear that it is of histology in its growing zone that I wish to speak, We have passed through two phases of histology, through the primary analysis of its elements and of how they are put together to form organs and we have now a third and entirely new type of subject- matter. There is, it seems to me, no longer any need of an elementary course in histology, in a medical school for which the entering students have been ade- quately prepared in biology and in the use of the microscope. I am well aware that many of you may not agree with this idea, but it is my real conviction. | How else shall we progress in education unless we condense those things which have become so well known that they have been simplified and teach knowl- edge in its growing zone. By an elementary course in histology, I mean one in which the major part of the work consists in learning to describe and identify sections; this is the finished part of our subject, not its zone of growth. The subject-matter of this part is simple, is well worked out in text-books and can be readily mastered by the student without much aid. It seems to me that, in each subject taught to advanced students, the teacher should make a clear analysis in his own mind of that part of the subject-matter which is static, well known, well presented in text-books, and hence readily available to the students’ own in- itiative, and that part which is dynamic, concerning which there are marked differences in opinion by ex- perts, and concerning which he may confidently expect development in the coming years. There are assuredly dangers involved in regarding any body of scientific knowledge as static, but at the risk of wearying you I wish to make quite specific the type of material which seems to me feasible subject-matter for a course in histology at the present time, and I will take four examples from my own experience. In presenting these examples, I have also in mind that when a ce!- tain foreign commission visited our laboratory to study our methods of teaching, it was clearly in the minds of our guests that, without the specific material of modern biology, histology was lacking in adequate subject-matter for medical students, The frank dis- cussion of such differences in plans for education I consider of value to teachers; it is obvious that we would give modern biology as the preparation for histology. My first example will be the spleen. In the first place, I would give to each student a section of human spleen and of the spleen of one or two animal types yay 15, 1925] in advance. It has been our custom to give the sec- tions to be stained and mounted by the students at the close of the period before the subject is taken up in class; that assures ample material in the way of sections to be used for reference. For the work on the spleen the student would have, in his own collec- tion, not only sections of the spleen but also of hemal glands and of lymph glands. Moreover, one of his sections would be a mesenteric lymph gland in which ne had filled the lymphatic sinuses with ink by inject- ing the lymphatic vessels of the intestine. The spe- ejfic work on the spleen would then be directed toward. three ideas—what is the nature of the circulation in the spleen, what kind of endothelium lines its veins and what are the free cells in its pulp. Not one of these problems can be analyzed without experiment. I should begin with Mall’s erucial experiment to understand the remarkable nature of the splenic cir- culation. To prepare the material, take a dog the day before the class exercise and tie off all the splenic veins, slip the organ back into the abdominal cavity for half an hour, at the end of which time the animal will have bled into its own spleen until the organ is twice its normal size. Then tie off the arteries and fix the entire organ in formalin without any rupture of its capsule, A second similar experiment, in which all the vessels are cut before fixation brings the organ back to the normal size, very quickly makes a con- vincing comparison, The class then would have frozen sections made from the two experiments; in one, both the pulp and the veins of the pulp will be engorged with blood; in the other both will be empty. This, then, would give the material from which to discuss how the splenic pulp can be so completely filled and then so quickly emptied. In a lecture one could then show why the question of whether there were specialized channels in the pulp between the arteries and the veins of the pulp dominated research on the spleen so long and how the work of Weiden- reich and Mall had finally demonstrated that it is the splenic pulp as a whole that intervenes between artery and vein. In the frozen sections of such material there will be occasional places in which the blood has run out of a vein of the pulp, and such places can be used to illustrate the contrast between the pulp and its veins; but for this purpose we have in Baltimore some beautiful complete injections of the veins of the splenic pulp, made by Dr. Mall and never illustrated in his publication. In these preparations he succeeded in filling the pulp so completely with one substance and the veins with another that both are quite distinct. Our next topic would be the nature of the endo- thelium lining the ampullae and the veins of the pulp; and here we would use the technique introduced by Mollier, who has shown that, when the spleen is fixed SCIENCE 501 after a moderate distention produced by circulating the fixing fluid throngh the organ and the sections stained with an intense protoplasmic dye, such as acid fuchsin, the endothelial lining of the veins can be seen to be riddled with holes. Each student would receive such a section for his collection and could then find for himself the peculiar, widely fenestrated endo- thelium of the veins of the splenic pulp and could then more easily understand from such evidence how the animal can bleed into the splenic pulp and then empty the pulp so completely. We would give out one section in which a very little ink or Prussian blue had been injected in one quick spurt into the splenic artery. Such an injection of the splenic arteries rep- resents an extravasation, if you will, into the splenic pulp, or in other words shows that the splenie pulp is in lieu of a capillary bed. These points we regard as feasible to demonstrate and that after such a pres- entation of the nature of the entirely unique circula- tion of the spleen, an organ in which there is nothing but a framework and a vascular bed, the student could take an ordinary section of the spleen, find its trabecu- lae and think of the meaning of its bands of muscle, identify the Malphigian corpuscles and see for him- self why it is that the relation of the splenic pulp to the veins of the pulp can not be analyzed from the study of normal sections alone. We would give one more preparation of the spleen, perhaps one of the most instructive, namely, a section of a spleen from a rabbit which had received repeated injections of trypan blue, or better of earmine, until the veins of the splenic pulp had become so clogged with cells, in our view, endothelial phagocytes or clas- motocytes, that the veins stand out in a section even when seen with the low power of a microscope. Here we would help the student to follow the endothelium of the sinuses and to see the clasmatocytes both within the sinuses and free in the pulp and then give him a chance to make his own judgment as to whether Aschoff’s term of “reticulo-endothelial apparatus” is significant or confusing. We believe that reticulum and the free endothelial derivatives are both quite dis- tinct in the pulp, but the student will surely find that the concept of a reticulo-endothelial apparatus so dominates opinion in pathology to-day that he may well spend much time in studying this section and getting his own ideas on this subject. The second topie which I wish to present is the nature of the cells of the connective tissues as they can be analyzed by the vital technique. Here I should begin with the experiment of Professor Maximow in the analysis of the fibroblasts from the clasmatocytes of the diffuse connective tissues by the use of vital neutral red. In the work which Dr. Cunningham, Dr. Doan and I have just published on the cells of the 502 connective tissues, we have given a technique for studying the living cells of the splenic pulp. If one takes a finely drawn out glass pipetie and plunges it into the spleen of a rabbit while the circulation is active, blood and free cells will run up into the pipette and one can then make a preparation entirely comparable to a blood film. These are made either on a coverslip for fixing and staining with the ordinary technique, or on a slide which has been coated with a film of vital neutral red and Janus green combined. In such a preparation from the spleen the cells will differ according to whether the pipette entered the pulp or a follicle. If the specimen comes from a follicle, lymphocytes will predominate, but if from the pulp, then there will be two predominating types of cells, the large free clasmatocytes, filled with red blood-cells or their débris, and the monocytes with their beautifully stained rosettes and outlying mito- chondria. This is not an easy technique to give a large class, because the spleen will not stand an unlimited number of such punctures, but one animal may be used for about fifteen students. These two types of cells, the clasmatocyte and monocyte, can perhaps be most easily demonstrated to a large class by making a vital film from a seraping of a freshly cut surface of the lung. For this experiment we should inject a little ink with a hypodermic needle into the trachea of a guinea pig the day before, following the work of Dr. Wislocki, and from this material we should find no difficulty in securing for every student a suc- cessful preparation. I may say in passing that the method of puncture entirely solves the question of giving a class. good films of bone marrow,. both for fresh material and for fixed smears. It does not mat- ter in the least that in our own laboratory there are two opposing views concerning the interpretation of such specimens, we believing that the clasmatocytes and monocytes represent two different functional strains of cells, while Dr. and Mrs. Lewis believe that they are one strain. Indeed such differences in inter- pretations are as stimulating and valuable to our stu- dents as they are to ourselves. When you can bring out such points of difference of real significance to the study of what cells actually do, then the student: knows that he is studying a growing. zone of medi- cine. Such differences are only of value to a student when both points of view are presented to him with entire fairness. For our own work we regard that the separation of these two strains of the cells of the connective tissue is of value because we were also working on tuberculosis last spring and obtained evi- dence which convinced us that it is specifically the’ monocyte which becomes the epitheloid cell in tuber- eulosis. This concept seems to us to open up an entirely new range of experimentation in connection SCIENCE [Vou. LXI, No. 1595 with tuberculosis, in which it will be possible to sur. vey the whole subject of the relationship of clasma. tocytes, monocytes and lymphocytes in this disease, The next subject which I wish to discuss is the teaching of the pancreas. Here we would follow the work of Dr. Bensley. We would give our student sections of the pancreas, selected in different func. tional states, as Dr. Bensley has taught us, to show the maximum of the basophilic substance and the maximum of zymogen granules. For the class work we would give a bit of the fresh pancreas of a rab- bit, and sometimes a second preparation after an in- jection of pilocarpin to show an emptying of the zymogen granules. We would then give the pancreas of the guinea pig with the vital injection of neutral red for the islets, have the experiment of the count- ing of a small bit of the organ, and hunt for the individual islet cells either in the septa or from more completely teased bits of the tissue. On the next day we would give the vital injection of the Janus green for the mitochondria, the beautiful demonstration of the controacinar cells by the injection of methylene blue and finally the mixed injection of pyronin and Janus green. Ever since Dr. Bensley published his studies on the pancreas we have tried for a satisfac- tory demonstration of the blind ducts to the islets, and this year we got such a clear demonstration of the point that no student could miss it. By chance we made an injection of the pyronin of double strength combined with Janus green and let the prep- aration stand a half hour; then every islet was clearly stained in the Janus green and the plexus of the ducts stood out beautifully distinct in the pale red of the pyronin, I think that no student could look at the demonstration of the living centroacinar cells with their processes reaching far out between the acinar cells without realizing how inadequate ordinary sec- tions are to demonstrate them. After a student has made such a study of living pancreatic cells, sections may seem a little dull to him, but they will serve to remind him of what the pancreas really looks like and we are confident that the student would still have some vivid memories of the real organ in his mind to aid him in physiology and pathology. The fourth illustration which I wish to give is from the reproductive system. Our material for this sub- ject would depend on the work of Ancel and Bouin, Stockart, Evans and Long, and Corner. It happe?s that the laboratory in Baltimore is near a slaughter house and so an abundant supply of material from the pig is available. We would give each student or each two students an entire uterus and ovaries from a Plt: Then, following the work of Corner, we would have each student study the ovary with reference to its condition in the oestrous cycle and whenever an ovary yay 15, 1925] was found with a recently ruptured follicle, the tubes or the uterus would be washed out by Corner’s tech- nique and the ova recovered. Frozen sections would pe made from a corpus luteum selected to show the ereatest amount of fat and the sections stained with Sudan THI. On the next day each student would receive a pregnant uterus and study the foetal mem- pranes and placentation. In our course this day’s work was developed by Dr. Wislocki, who gave a demonstration of comparative placentation from his own work. Each person teaching in a course should thus enrich it with the material of his own research, After such a study in the laboratory the student would not find it hard to study sections of ovaries; all sections of the ovary and of the uterus of what- ever animal used should now be given out with a record of what phase in the cycle they represent. It seems to me anatomists have contributed more in the past few years to the analysis of the reproductive cycle than all clinical experience put together. I trust that you will pardon the detail with which I have given these illustrations; they show how the material for a course in histology can be built up from research and they represent material that is entirely feasible from the standpoint of experience. It is all readily obtained and not too difficult to ana- lyze. I have intended these examples to show the difference between an elementary and an advanced course in histology. Such plans for material I am convinced should be frequently changed in any course, if it is to have life and vigor. Sometimes a. wholly new arrangement of the sequence of a course will: give new plans of presentation, or a new technique | will develop in research that will give a whole new. Material should be frequently: range of material. dropped from a course and new specimens brought in. In a word, it is of more importance that the material of a course should be thoroughly interesting to the teacher himself than that he should try to cover the entire ground of his subject each year. I am quite aware that besides the general criticism of this concept of the type of course in histology, there will be the direct criticism of the ‘pathologist that in such a course the student does not get’ such 2 specific knowledge of the characteristics of normal human material as to give him a nice discrimination of early pathological changes. In this connection it is my judgment that courses should not be too closely dovetailed because in the medical school the student gains by having similar subjects from different view- Points. I think that the histologist can better afford to use sections from different animals so selected as to demonstrate function in the clearest way possible or else selected to show variations in structures of the different experimental animals, such as the marked SCIENCE 503 variation of bronchial musculature, that are at the present time significant in medical research and leave to the pathologist the human material, over which he has such a vastly greater control and concerning which he is almost certainly more competent to judge. Tt has come to my attention in late years that the directors of physical training in all secondary schools, even those for girls, receive a higher salary than any of the very most successful of those teachers who are concerned only with the intellectual side of education. I have finally found some comfort in this unweleome fact in the thought that at least no teacher of physical exercise commits the cardinal sin of thinking that he can develop the muscles of his students for them by exercising his own muscles. I want to stress the idea that the value of a laboratory to the student is that it is a place where he can work. The student could get facts more quickly out of a book; a text-book that tends to take a student away from his microscope is a poor aid to a course in histology. Moreover, the teacher does not need to point out to the student the things in his section which the student can find for himself. For example, when the student is studying blood-vessels the teacher may show him a corrosion of the organ and call his attention to the number of orders of vessels in a given layer; he should show him how to dissect with the focusing screw of the microscope the coats of vessels in some such mem- brane as the pia mater, but he does not need to find for him the vessels in sections. Most of all the teacher does not need to concern himself with aiding the stu- dent to memorize; for that the student can be entirely responsible himself. If I were to give a young teacher advice concerning the directing of a laboratory course, it would be this; see that the material is carefully chosen and excellent in quality before it is given out, remember most of all that the period of laboratory belongs to the student for his work; when you do dem- onstrate to a student let it be to show him that there is much more in his material than he has been seeing, that research involves careful observations and rec- ords as well as interpretation, and when you leave him be sure that he has a fresh impetus for his own work. There is a double problem in all medical teaching; medical schools are founded to train physicians, who shall practice medicine, and research workers, who shall advance medical science; that these two groups are not entirely distinct all medical history attests. I do not minimize the importance of training prac- titioners of medicine, indeed in all schools they make the larger group of the students, but it is entirely clear that unless teachers of medicine attract and train those who are to be teachers in the next genera- tion, the profession will die at its source. But, while any given school will train only a small percentage 504 of its students to become professional investigators, nevertheless all teaching in the sciences can and ‘should depend on the methods of research. All the class can be taught in the spirit of research, which means that it is more important for the student to be able to find out something for himself than to mem- orize what someone else has said. Does any one doubt that this principle applies to diagnosis? Certainly in the practice of medicine every case is a problem; and therefore a plan of instruction for the practice of medicine that allows great range for the idea of solv- ing problems must be the ideal one. The knowledge of what has been done must play a large réle in the training for any profession; nevertheless, the ability to solve a problem is so much more difficult to acquire than the ability to memorize facts that education should stress the one even at the expense of the other. Indeed the facts which one remembers from one’s own experience or from the experience of one’s profession are merely the tools with which to work. The ability to catch the imagination of young peo- ple and direct their interests toward research is quite a special gift in a teacher and each school must have some members of its staff who enjoy this type of teaching if that school is to contribute toward the training of research workers. In the days when I first started the study of medicine, the attitude to- ward the research student was entirely different from what it is now. Then, from the student’s standpoint, it was unpopular to do research, and the one who undertook it had little sympathy either from his home or from his fellow-students. At present most of the outside influences to be summed up under public opinion favor research. Nevertheless, I believe that the best method of getting students interested in re- search is now the same as it was then, namely, through an interest in ideas presented by a teacher who has the power to catch the imagination of the gifted stu- dent. It may be that the student will apply for re- search, it may be that the teacher will suggest a problem to a student, but it is essential that student and teacher shall be in sympathetic understanding. The extent to which the student’s mind will be turned toward research is in direct relation to the quality of intellectual leadership on the part of the teacher; this quality is brought out both in lectures and in informal discussions with students. In connection with lectures it is my fixed opinion that they should be few in number and that they should not aim at giving any comprehensive body of approved facts such as are rightly set down in text-books, but they should deal with the ideas in which the subject is growing.