THE PROTOPLASM THEORY: 
AN INTRODUCTORY LECTURE 
DELIVERED AT THE OPENING OF THE WINTER SESSION OF THE COLLEGE OF 
PHYSICIANS AND SURGEONS, NEW YORK, OCTOBER 1, 16!3. 
Di 
EDWARD CURTIS, A.M., M.D., 
PB0FEK80R OF MATEBIA MEDICA AMD THEKAPEUTICS. 
'Published by the Medical Class 
NEW YOKE: 
CHAS. E. WILBOUR, PRINTER AND BOOKBINDER, 
205-213 East Twelfth Street. 
1873. THE PROTOPLASM THEORY: 
AN INTRODUCTORY LECTURE 
DELIVERED AT THE OPENING OP THE WINTER SESSION OP THE COLLEGE OF 
PHYSICIANS AND SURGEONS, NEW YORK, OCTOBER 1, 1873. 
BY 
EDWARD CURTIS, A.M., M.D., 
PEOFESSOE OF MATEBIA MEDICA AND IHEBAPEFIICS. 
Published by the Medical Class. 
NEW YORK: 
CHAS. E. WILBOUR, PRINTER AND BOOKBINDER, 
205-213 East Twelfth Street. 
1873. College of Physicians and Surgeons, 
New York, October 18, 1873. 
Dr. Edward Curtis : 
Dear Sir :—We take great pleasure in acquainting you with the following 
resolution, which was passed at a meeting of the medical class of the present 
Winter Session: 
“ That a committee of three be appointed to carry out the necessary 
arrangements for the publication of the introductory lecture of Prof. Edward 
Curtis, delivered on the evening of October 1, 1878.” 
We would not consider the duty which this resolution imposes upon us, as 
representatives of the class, fully performed, if, while we most respectfully 
beg that your manuscript be placed in our hands, we did not at the same time 
convey to you the satisfaction with which the resolution was received and the 
generosity with which it was sustained by the united medical class. 
We remain, most respectfully yours, 
A. P. Zenansky, 
L. L. Danforth, 
J. E. Stillwell, 
Committee. 
27 Washington Place, New York, 
October 20, 1873. 
Messrs. A. P. Zenansky, L. L. Danforth, J. E. Stillwell : 
Gentlemen:—It will give me great pleasure to accede to the flattering 
request of the medical class to publish my introductory address, and the 
manuscript is at your disposal for the purpose. 
Very truly yours, 
Edward Curtis. THE PROTOPLASM THEORY. 
Gentlemen :—The pursuit upon which you enter to-night 
centres around the study of that mysterious condition, life, as 
shown in the highest of created things, man. The structure 
of the human frame, the working of its different parts, the 
changes constituting disease, all form the practical objects of 
your chosen study. 
But man, viewed as an apimal, is not a wholly unique crea- 
tion. lie is but one member of a great family, and partakes 
of the family characteristics. Hence it happens that many 
features of human anatomy and physiology are unintelligible 
by themselves, but become pregnant with meaning when under- 
stood as the expression of some general type—some family trait 
of the great brotherhood of living things. There is, then, really, 
but one science of life, and its general laws must be studied if 
we would understand the meaning of the facts presented by 
any single form of living thing. For biology, as this science 
is called, is in this respect like a figured woven fabric. View 
the texture as a whole, and in the colors stamped on its face 
there appears an artistic design. But unravel warp from woof 
and examine the tints on each separate thread by itself, and 
you see but meaningless daubs. 
I can think, then, of no more fitting subject for a prefatory 
lecture than to lay before you one of the fundamental questions 
of biology, sketch for you the evidence bearing on its answer, 6 
and present you with tlie result. Thus you will learn a lesson 
in the method of investigation in natural science, and at the 
same time become practically acquainted with facts which it 
is important you should know, as lying at the foundation of 
anatomy, physiology, and pathology. 
The ultimate aim of biology is to know what is life ; how 
are its phenomena produced, and what is the true history of 
life-display on earth. The answers to these questions, if found 
at all, will be got only from a faithful study of nature. And 
the first step in the problem is—what % 
Suppose an arithmetician is set the task of extracting the 
square root of a given number. If it be a whole number, he 
proceeds at once to the operation. But if instead it be a string 
of mixed numbers and fractions, he must, as a preliminary 
step, find a single expression for their sum. This he does by 
reducing all the terms to simple fractions, aud all these to a 
common denominator. Adding, then, the now similar terms, 
he obtains a single fraction that is the equivalent of the whole, 
and upon this he operates as upon an original simple number. 
So is it with the biologist. His problem is to extract the 
square root of life, not of one living form, but of the whole 
vast array of animals and plants in all their endless variety. 
He therefore has the same preliminary step to take as the 
arithmetician: to reduce all diversity of form and faculty of 
living things to a similar mode of expression—to find, in short, 
the common denominator of life. 
And this problem is our theme to-night. Weigh well now 
its full import—its far-reaching scope. For it means no less 
than a daring search for a single substance as the material 
basis of all living forms : a single mode of performance of the 
several vital functions, and a single underlying general plan in 
the varied architecture of the animate world. And all this, 
too, not merely between allied forms, as dog and wolf, fir and 
pine-tree, but between all things whatever that live, animal and 
vegetable together ; between man and the giant forest tree, and 
between both and the living specks that form the scum on a 
puddle of ditch-water. 
T et, wild and improbable as seems the idea, it is the proud boast of tlie biologist to say to-day, it is realized: this com- 
munity does exist; after two centuries of patient labor a 
common denominator of life has been found. 
Before examining the evidence on which this sweeping state- 
ment rests, let us first be sure that we have a correct idea of 
the nature of the thing with which we deal. Our theme is 
living creatures—living matter. Xow, what do we mean by 
the word “ living ? ” The only answer we can give, in our 
ignorance, is this. Of life in the abstract we know nothing: 
we simply recognize a state of matter in which it is the seat of 
certain phenomena, and to this state we apply the term living. 
That is, all we know of life is the signs by which it shows 
itself. And these signs, or essential vital phenomena, that is, 
such as are common to everything recognized as alive, are as 
follows: All living things nourish themselves, by which we 
mean that they renew their substance by converting outside 
material into their own. They also increase in bulk, or grow, 
by the same process. They reproduce their kind, and finally 
they display some form of what we may call vital activity, 
varving from mere sluggish movement in the lowest organisms 
to the complex functions of the human body and mind. Yet 
diverse as are these acts, they are but different expressions of 
a single faculty of living matter, power to determine mole- 
cular movement among its particles. For it is a well-ascer- 
tained fact in physiology that every vital act whatsover, be it 
motion, secretion, or the lofty exercise of thought and reason, 
are all accomplished at the expense of physical or chemical 
change in the living substance ; or, as we may express it singly, 
have all their determining cause in some mode of motion of the 
particles of living matter. To sum up, then, we mean by living 
matter such as can nourish, grow, reproduce, and in some 
additional mode display molecular movement. 
We pass now to our main subject, the alleged discovery that 
throughout all nature there is but one kind of living matter 
that executes the functions just detailed, and but one general 
method, severally, of their performance. 
Our first step is plainly to get the tyjoe of this universal mat- 
ter and method, and since we seek what is the common property 
7 8 
of all living tilings, it is equally clear that we shall find the 
purest type in the lowest creature on the scale, where the phe- 
nomena of life occur under the simplest form. 
Sail out with me then upon the broad Atlantic. Let us heave 
to where the sea is deepest—where the ocean-bed lies miles be- 
low the vessel’s keel. We will then cast the lead with a line sev- 
eral thousand fathoms long. It will sink into abysses where the 
water is ice-cold and motionless—the darkness eternal: yet on 
its return from those profound depths we shall very likely find 
both lead and several feet of the line smeared with a slimy 
ooze which the haul through more than two miles of water has 
failed to wash off. Repeat the sounding at another spot a hun- 
dred miles or more away, and the result will very probably 
be the same, showing that the deep sea-bed for hundreds of 
square miles contains as an ingredient of its oozy mud this sticky 
material. To the naked eye this stuff is a structureless semi-solid 
slime. Under the microscope it is seen not to be a continuous 
mass, but a collection of separate irregular bits or clumps and 
net-works, which, however, are still utterly devoid of structure 
—are mere shapeless specks of slime. 
Yet is this slimy matter alive as we are alive, and the arche- 
type of the basis-substance of all animate beings : these formless 
flakes living individuals as ourselves, and their simple life-acts 
an epitome of the vital phenomena of each and everything that 
lives. In other words, startling as it may seem, here out of the 
oozy mud of the Atlantic basin we have that pure type of the 
matter and method of life that we seek. 
Let us then carefully studv these lowliest of living things. I 
premise by telling you that there are several genera of these 
structureless denizens of the sea known to naturalists. The va- 
riety just mentioned, Bathybius, as it is called, which is found in 
such vast quantity in the uttermost depths of the ocean, is by far 
the most interesting and suggestive. But yet it has been less 
thoroughly studied than other species in the details of its life- 
history. As I wish therefore to tell you nothing that has not 
been actually seen, I shall refer in the following descriptions to 
better known species of the group, found in more accessible lo- 
calities. As it is convenient also to have names for what we are 9 
talking about, I will tell you that these objects as a class are 
called the Monera, and we may anglicize the name and speak 
of an individual as a moner, as we would say a horse or a dog. 
Let us now imagine one of these minute living moners to be 
in the field of the microscope, lying free in a little of its native 
sea-water. What do we see ? Apparently an irregular spatter 
of semi-fluid material, colorless and transparent, but containing 
a great number of minute particles giving it a granular look. 
Definite shape it has none, other than that it consists of a cen- 
tral mass from which radiate in all directionsMelicate branch- 
ing and anastomosing threads. But all is homogeneous:—cen- 
tral portion and branches are one continuous mass. Through- 
out the whole there is not the slightest sign of structure, of dis- 
tinct parts or organs ; not even a difference in density between 
the outer and inner layers of substance. The whole appearance 
is in miniature what might be formed by a spoonful of granular 
mucilage dropped on a table from a height, and spread out by 
the force of the fall into a radiating spatter. 
As to composition, the mucus-like substance of the moner, 
tested chemically, is found to be an albuminous matter, and to 
behave in a peculiar way with certain reagents. 
To determine next the vital endowments of the living mass 
before us, let us take our seat at the microscope and carefully 
watch it. The first thing that will strike the eye is that the ob- 
ject is in incessant motion. Its outline is constantly changing, 
and the fine mucous threads ceaselessly lengthening, shortening, 
separating from one another and reuniting, appearing and 
disappearing on the surface of the central mass. But more 
remarkable even than this outward change of form is the rest- 
less activity of the substance within itself. Currents are 
moving up and down, right and left, throughout both body and 
branches, their direction indeterminate and frequently chang- 
ing. The semi-liquid material thus endlessly courses through, 
channels opening within itself, as water flows through water 
where the Gulf-stream meets the sea. 
Here then we have that fundamental life-act, spontaneous 
movement, plainly performed under our very eyes. And 
throughout nature there is nothing more marvellous than this. 10 
same sight of a formless matter, structureless, naked and free, 
spontaneously heaving, quivering, and streaming in and through 
itself, like molten glass stirred by invisible hands. There is a 
fascination in the sight, too, as in watching the ocean surf 
break on shore; for here as there we cannot escape a feeling 
of awe at thus confronting the workings of an intangible 
energy, self-contained yet equally distributed throughout the 
moving mass, wasteful yet unconsumable in its ceaseless display. 
And indeed in the complex movements of the moner we have 
actually reproduced the phenomena of the ocean, as though the 
stormy Atlantic had imbued this humblest of its denizens with 
its own eternal restlessness. The heaving billows, the never- 
ending internal agitation and intermingling of waters by cur- 
rents and tides, are all pictured in tiny miniature in the self- 
imposed turmoil of the living mass before us. 
But suppose, while we are watching this wonderful sight, 
there happens to be wafted against the moner another dweller 
of the sea,—an object called a diatom, a microscopic vegetable 
organism encased in a delicate shell of flint. Instantly there is 
method in the hitherto seemingly objectless movements of the 
moner, and he proceeds forthwith to literally put himself out- 
side of the intruder. No sooner does the diatom touch one of 
the moner’s gelatinous threads than it is held by the stickiness 
of the mucus-like substance, and at once both this filament and 
its neighbors begin to thicken by an influx of matter from the 
main body. At the same time they gradually fuse together 
until they form a thick continuous layer, which slowly extends 
itself around the helpless diatom. This envelopment accom- 
plished, the mass retracts, carrying its prey with it, until the 
latter is drawn down into the central portion of the moner’s 
substance. Here it remains a certain time, but is at length 
pushed out again by reversal of the process by which it was 
captured. Yet if we look closely at the diatom now, we shall 
find that it is only the shell that is cast away, the soft contents 
having been quietly drawn off and retained in the moner’s body. 
Moreover, if we supply young moners plentifully with diatoms 
we shall see them rapidly gain in bulk from day to day, show- 
ing that the matter thus taken into the moner’s body becomes in- 11 
sensibly changed there into new living moner-substance. In 
other words, we have again been witnessing the performance of 
one of our fundamental vital functions; namely, the combined 
act of nourishing and growing. 
One other feat and one oidy, but that a very simple one, will 
be enacted by our little friend. At some time in his career we 
shall chance to see a furrow form around his central mass, 
which, gradually deepening, ends by splitting him in two. 
What is the result—death ? Hot at all: on the contrary, the 
effect is that whereas we before had one morier we now have 
two : for each of the divided halves soon takes on all the fea- 
tures of a perfect individual. In other species the reproduc- 
tive act, for such this plainly is, differs a little in detail. The 
moner draws in his branched network of threads until he be- 
comes a smooth round ball. Over this a thick, tough, transpa- 
rent envelope forms, and thus enclosed the round mass gra- 
dually splits up into a considerable number of smaller ones. 
Each of these then develops a tail-like appendage : the invest- 
ing envelope bursts: and the new brood come swarming out 
like young tadpoles, being driven swiftly about by lashing of 
their tails. But they do not keep this form long : for the day 
after they are first set free they already begin to change to the 
parent type, a change that finally becomes complete. In this 
species, thus, the parent, instead of dividing into two, splits up 
into a number of new individuals. 
In still other organisms we have two alternating modes of 
reproduction. After several generations produced by simple 
division, two individuals meet and actually fuse together. The 
mass thus formed becomes encysted as in the moner just de- 
scribed, and after a while the envelope bursts and the entire 
contents flow out as a countless swarm of excessively minute 
specks, so small that the very highest powers of the microscope 
are needed to see them at all. These infinitesimal specks can 
then be watched and actually seen to grow into the likeness of 
their parent. 
Such is the simple life-history of the monera, and now let us 
sum up what we have learned by its study. We have seen a 
purely homogeneous substance—a mere structureless mass of 12 
matter, perform under our eyes the great vital functions of 
movement, nutrition, growth and reproduction. We thus learn 
the important fact that life does not necessarily require for its 
display any structure in the individual, hut all its essential 
functions in their simplest manifestation can be equally pei- 
forined by one homogeneous matter. Thus the structureless 
moner, the simplest known, is at the same time the simplest 
conceivable type of a living individual. 
Next as to the substance itself, we find it to be a colorless, 
transparent, viscid, albuminous matter. As regards the manner 
of performance of the several vital functions, we see movement 
executed indiscriminately by all the particles of the mass : nutri- 
tion and growth effected by the living matter putting itself 
bodily around the article of food, and then transforming this 
into its own substance : and reproduction accomplished by the 
body of the parent dividing directly into new individuals or 
germs. 
Such then are the matter and method of life of the monera : 
and now let us jump at once to the highest of created organ- 
isms, the vertebrate animals, among which we ourselves take 
rank, and see how their complex structure and functions con- 
form to the type we have been studying. 
Prick your finger and examine a drop of blood under the 
microscope. It consists of a colorless fluid, in which float vast 
numbers of minute bodies. Most of these are the reddish disk- 
shaped corpuscles, as they are called, that give blood its red color. 
Put besides these, though much fewer in number, are rather 
larger bodies of—mark now the words—a colorless, transpa- 
rent, granular, semi-liquid and viscid substance. At first these 
objects appear as mere motionless balls; but if you prevent the 
drop of blood from evaporating, and keep it artificially warmed 
to the natural temperature of the bod}7, or, what is far better, 
if you take a drop of frog’s or newt’s blood, which does not 
need warming, you will soon be the witness of a most striking 
and wonderful exhibition. The motionless sphere awakes as it 
w7ere from a swoon, and begins to show signs of life. Its parti- 
cles begin to move upon each other ; the round outline is lost, 
and the body, or corpuscle, as it is called, assumes constantly 13 
changing and most fantastic shapes, and moves actively about 
in the field of the microscope. Now it throws ont from its sub- 
stance a dozen fine gelatinous threads, and holding by their sticky 
tips to the surface of the glass slide, retracts upon them, using 
them thus as agents for locomotion. Again, it divides into two 
portions connected by a long slender filament. These move off 
in opposite directions and writhe about independently, until 
apparently tired of being Siamese twins, they approach each 
other, while the connecting thread shortens and thickens, and 
finally meeting, fuse once more into a single mass. If the cor- 
puscle meet a large object, it spreads out into a thin flat layer 
a id creeps over it in that form. If it come upon a narrow 
channel, such as is often left between masses of red corpuscles, 
it squeezes through like sand in an hour-glass. In fact there is 
no end to the protean changes of form that this extraordinary 
little organism can assume. 
Next perform the following experiment:—Take your drop of 
frog’s blood and add to it a little of a fine insoluble powder, as 
indigo or charcoal, and you will soon see some of these same 
white blood-corpuscles with one or more grains of the powder 
embedded in their substance. Moreover, they have been seen 
with broken fragments of their companion red corpuscles simi- 
larly embedded. 
Again, warm slightly the slide holding your drop of frog’s 
blood. The movements described become more active, and if 
you combine good fortune with patience you may see furrows 
form, disappear and reform on the surface of a corpuscle, until 
at last one extends completely through, and the little body is 
split in two. Each half then moves about actively and presents 
all the features of a perfect individual. 
Finally, test these bodies chemically, and you get an albumi- 
nous substance reacting precisely like that of the monera. 
Now, in this sketch I need not dilate on the points of resem- 
blance between these little corpuscles of the blood and the mo- 
nera. They are startlingly self-evident. Both are composed 
of the same kind of substance, have the same physical charac- 
ter, and perform identical vital acts in a generally similar man- 
ner. There is, however, one point of difference between the 14 
two. The substance of the moner is perfectly homogeneous, 
but embedded in that of the white blood-corpuscle are one or 
more small roundish bodies with well-marked outline. These 
we call nuclei, but of their function and vital significance we 
know nothing. 
"VVe find, then, as the first result of our study of vertebrates, 
that in their blood, and I may add in the lymph also and sev- 
eral of the tissues, there occur independent freely moving or- 
ganisms, closely resembling the monera in all important par- 
ticulars. 
But yet these corpuscles we have been describing form a very 
small part of the bulk of vertebrate animals. What of the solid 
tissues ? How do they conform to the moner-type of life % 
Cut out the cornea from the eye of a living or freshly-killed 
frog and examine it immersed in aqueous humor under the mi- 
croscope. At first the tissue is perfectly transparent and homo- 
geneous ; but after awhile there makes its appearance a net- 
work of oval nucleated masses with long slender branching arms 
or processes—the whole composed of a finely granular but color- 
less and transparent substance. Ho further words are needed 
to call up our humble friend the moner vividly before our eyes. 
For were it not for the large nucleus, these present bodies, with 
their soft granular substance and delicate threadlike processes, 
could easily be imagined to be moners that had crawled into 
the cornea while the frog was asleep, so close is the outward 
likeness. Chemistry, too, could be called upon to support the 
fancy, for once more reagents show in the transparent matter 
of these corneal corpuscles, as we call them, the albuminous 
substance of the monera. You will naturally, then, if you are 
enthusiastic, keep your seat at the microscope and confidently 
watch for vital movements and reproductive activity on the part 
of these bodies. But, alas! you will be wofully disappointed. 
You may watch till your eyes ache with weariness, or till the 
tissue decomposes, but these pseudo-moners embedded in the 
substance of the cornea are as motionless as statues. Hot 
a sign of any movement or division for reproduction will occur. 
But be not too easily thrown off the scent. Bemember the im- 
portant fact, that in the adult the fixed tissues are fully formed. 15 
Active movement, growth, and multiplication of adult anatom- 
ical elements could therefore hardly he expected to take place, 
and it would be illogical to deny these elements functional 
power merely because they do not constantly exercise it. How, 
then, shall we decide upon the vital endowments of these cor- 
puscles of the cornea ? 
You all know of the process called inflammation, and those 
of you at least who have been here before will call to mind 
that it in part consists in unusual formative activity, whereby 
actual organization and growth of new tissue may result at 
the inflamed spot. Let us then excite in a frog’s cornea this 
abnormal activity; that is, inflame it, and see what picture the 
microscope will yield. Take a living frog and cauterize the 
centre of the cornea with a pointed stick of nitrate of silver, 
and after a few hours remove the part and examine as before. 
Nothing is more convincing than the picture now seen. The 
inflammation set on foot by the cautery has aroused a sleeping 
energy in those hitherto motionless corpuscles, and once more 
we have the old story repeated. Slow but distinct movement 
can be seen agitating the granular masses; they have drawn in 
their processes ; have changed their form, and in many cases, 
if we have waited long enough after the cauterization before 
removing the cornea, we will And a group of smaller new 
bodies within the boundary of what was before a single one. 
In other words, in these fixed anatomical elements of the 
cornea we have again an example of masses of living sub- 
stance, which physically, chemically, and vitally conform to 
the type of the monera. And to make a long story short, in 
other tissues of the body, as bone, cartilage, glands, epithelium, 
gray nerve substance, we have, as here in the cornea, nucleated 
masses of a soft albuminous material forming a prominent 
element of their structure. 
But still our task is not done: these albuminous bodies or 
corpuscles, as we may for the present call them, form still 
but a small proportion of the bulk of most of the tissues. 
Bundles of fine fibres in the cornea, a dense, apparently 
homogeneous matrix in cartilage or bone, really compose the 
mass of the tissue, forming a solid substratum in which the 16 
soft corpuscles lie embedded; while in muscle and nerve fibres 
we have elaborate and special structures with but insignificant 
traces of any corpuscular elements. Now what of these fibres 
and matrix substances—these formed elements of tissue ? They 
present none of the physical, chemical, or vital properties of 
the moner-type; does this type then wholly fail in their life- 
history? The answer depends on which of the following 
possibilities is true. Either the formed elements are ge- 
netically distinct from the moner-like albuminous bodies 
associated with them in the tissue, or one has been formed out 
of and by the other. To settle the question, compare first a 
tissue, such as cartilage, from an adult and an embryo of the 
same animal. At once you will be struck by the following 
fact. In the adult the nucleated albuminous corpuscles are 
rather sparsely scattered through an abundant firm matrix: 
but in the embryo precisely the reverse obtains; the corpuscles 
compose almost the whole bulk of the tissue, lying closely 
packed, while the matrix substance is small in amount and 
rudimentary in character, consisting only of a thin shell of 
matrix-matter on the surface of each corpuscle. The in- 
terpretation of this fact is obvious, but let us without more 
ado go to the bottom of the matter and trace the general plan 
of tissue-development from the beginning. All animals, as 
you know, grow from ova or eggs, as plants from seeds. Now 
what is the egg of a vertebrate animal? You will weary of 
the words when I tell you that in the beginning it is nothing 
but a soft, granular, transparent, albuminous mass, containing a 
nucleus, and capable, as seen in some animals, of performing 
moner-like movement and change of form. Later in its 
career it becomes surrounded by or interpenetrated with 
nutrient material for its future use, and is encased in pro- 
tecting envelopes. "When impregnated and about to develop, 
the nucleus disappears, and the future animal is then, like the 
monera, but a homogeneous mass of albuminous matter. Next 
what ? Put freshly spawned frog’s eggs under the microscope 
and watch them continuously. After a few hours you will see 
sluggish movements of the egg-substance within its investing 
membrane. Then notches develop on its surface, which at 17 
first come and go, blit soon become permanent and pass into 
well-marked furrows. These extend and deepen, and at last, 
cutting entirely through, divide the egg-mass into several 
segments. These segments in turn divide, and by continu- 
ance of the process what was originally a single mass of living 
matter is now broken up into a great number of similar but 
smaller ones. 
During this process of division, nuclei reappear in the newly 
formed products of segmentation, so that the embryo now con- 
sists of an aggregation of nucleated masses of albuminous 
matter. But as this multiplication continues a differentiation 
begins; the successive generations of nucleated bodies arrange 
themselves into distinct layers, vary in shape, and propagate in 
such directions that form is given to the growing embryo. 
Still later, indications of the special structures of the adult tis- 
sues begin to show themselves, and now, by comparing embryos 
of different ages, the secret of tissue-building is revealed. In 
some the nucleated products of segmentation are transformed 
bodily into the peculiar structures of the tissue, as in muscle, 
where a single such nucleated body can be seen in all stages of 
gradual metamorphosis into a muscular fibre. In others the 
original nucleated masses persist as such, and the special 
tissue results from the formation around these bodies—and 
therefore by fair inference through their agency—of new 
material. Thus in cartilage we have successive shells of 
cartilage-matter forming around each original segmentation- 
mass of the embryo tissue, each new layer always forming 
within the old, until by firm cohesion of these shells there 
results the apparently homogeneous matrix of adult cartilage 
with its enclosed soft nucleated corpuscles. 
We see thus that in the beginning the entire animal is but 
a moner-like mass of living albuminous matter; that all the 
similar masses in the adult tissues are lineal descendants in un- 
broken series from this parent, and that it is out of or by the 
agency of these products of segmentation of the original egg- 
substance that all the complex structures of the adult tissues 
are formed. 
It remains only to inquire into the functional power of these 18 
same formed tissue-elements, such as muscle, nerve, and con- 
nective-tissue fibres, bone and cartilage matrix. We have 
already seen, by studying the corpuscles of the blood and 
cornea and the general development of the egg, that the 
moner-like bodies, or products of segmentation of the egg, 
possess at some stage of their career, at least, the pre-emi- 
nently vital faculties of moving, nourishing, growing, reproduc- 
ing and forming. Now do the fibres, membranes, and matrix 
substances of the adult tissues, formed out of or by the action 
of these nucleated masses, retain the same faculties ? You see 
at once how important is the answer. If it be no, it means that 
the functional power by which we recognize life belongs only 
to that one albuminous substance found in the monera, the 
animal egg and its nucleated offspring ; while if it be yes, it 
follows that we must at once give up as false all idea of a com- 
munity of actively living matter throughout nature. Well, the 
first case is the truth—the answer is universally no / whenever 
living matter departs widely from the type of the soft albumi- 
nous material so often described, and becomes differentiated 
into formed elements of structure, it loses forever the power of 
independent movement, of growing, reproducing, and forming. 
Never, in the repair of injuries, in inflammatory processes, or 
in morbid growths, do the formed anatomical elements take 
the slightest share in new productions of their own tissue, or 
show any other changes than degenerative ones. Even in the 
healthy economy their role is purely a passive one. Muscle is 
passively contractile only; nerve fibres conduct but cannot 
generate nerve-impulse; bone and cartilage matrix are but 
dense solid masses to furnish form and stability to the animal 
structure; and connective-tissue fibrils serve only to hold 
together adjoining parts. But wherever active function is to 
be performed— wherever the forces of nature are to be turned 
into life-work, there for the purpose we find collections of 
moner-substance—the nucleated descendants of the original 
egg-mass. Thus for secretion there are the glands, whose whole 
tissue is but an aggregation of such nucleated bodies with only 
the necessary connective tissue, blood-vessels, and nerves to 
bring them into relation with the rest of the system. For the 19 
elaboration of nerve-impulse, we have in the great nerve- 
centres and ganglia, directly connected with the nerve-fibres, 
soft nucleated corpuscles like those of the cornea, whose 
subtle molecular movements are the source alike of the power 
that harmonizes all the actions of the body, and of the still 
more mysterious operations of the intellect. 
1 have thus sketched for yon, somewhat disjointedly, it is true, 
the outline of such facts in the physiology of the higher animals 
as bear upon the problem we are studying, and I must ask you 
simply to take my word for it that, so far as observation goes, 
the fundamental principles we have developed hold good 
throughout the whole animate world—among all grades of ani- 
mal and vegetable forms. 
Let us now simply review the facts we have learned, and 
state them in abstract form, and we have what is called the 
Protoplasm Theory : a theory which I beg to remind you is in 
one sense no “theory” at all, inasmuch as it is simply a general 
statement of fact. We started, you remember, by asserting that 
the only definition we can give to living matter in general is 
that it is such as can nourish, grow, reproduce, and display some 
additional form of functional power reducible to molecular 
movement. Studying then the lowest and highest of created 
things, we found, as you will have seen, these somewhat start- 
ling facts. The essential vital functions are throughout all 
nature performed by only one kind of living matter, which is 
common to all animate forms, and is a homogeneous albuminous 
substance, of softisli consistence, colorless, transparent, and often 
containing little granules. Wherever found, this living matter 
presents essentially the same physical aspect, is substantially of 
the same chemical constitution, and performs the several vital 
acts after a common general method. We have discovered then 
what we may fairly call a universal matter of life. Let us give 
it a name : we do so, and call it protoplasm, or primitive form- 
ing material. 
But here allow me a word to save you from possible confu- 
sion of thought. Observe that the term “protoplasm” is 
applied only to the living matter as such, while possessed of 
the physical and vital characteristics peculiar to its condition: 20 
it is not the name of the albuminoid compound or compounds 
into which chemical analysis can resolve the living mass. The 
two conceptions are distinct and are fo each other as those of 
diamond and carbon. Diamond is wholly composed of carbon: 
yet while carbon is the chemical element wherever and however 
occurring, alone or in combination, diamond is the distinct 
thing—the gem-substance as such, characterized by peculiar 
lustre, transparency, hardness, and planes of cleavage. Disturb 
the crystalline condition that determines these physical attributes 
of the mineral, as by heating diamond, protected from the air, 
between the poles of a powerful battery, and though its chemi- 
cal composition is unchanged, yet the dull black mass into which 
the glittering jewel is transformed is, it is needless to say, no 
longer diamond. In other words, diamond is the mineralogist’s 
name for the crystalline gem, and carbon the chemical designa- 
tion of the matter that composes it. So with protoplasm : the 
word belongs not to the chemist as meaning a product of analy- 
sis, but to the biologist as the name of a living thing. 
To continue our summary, we find next as regards the mode 
in which protoplasm exists in nature, that it always occurs indi- 
vidualized into small distinct masses, which are generally, but 
not invariably, nucleated. In the lowest creatures, as the 
monera, and in the fecundated egg of even the highest organ- 
isms, a single such unit-mass of protoplasm constitutes the 
entire individual; while in the higher forms of life, where we 
have differentiation of parts or true structure, it is by the mul- 
tiplication of this same unit-mass of the egg and the more or 
less transformation of its progeny, that all the varied tissues are 
formed. In other words, throughout all grades of living things 
the nucleated or noil-nucleated mass of protoplasm is the typi- 
cal anatomical unit of form, as the brick or block of granite is 
the typical building-unit in masonry. All living organisms may 
thus be resolved into one or an number of these 
elementary units, simple or variously modified and transformed ; 
just as all masonry-work can be considered as a pile of the 
building elements cemented together and arranged in special 
manner. Having thus a distinct conception of the unit-mass of 
protoplasm as the fundamental structural element of life-forms, 21 
* 
let us give iia name. We do so, and call it—I regret to say— 
a cell. Why this name, you will ask : for you perceive at once 
that it is a complete misnomer: there is nothing whatever 
“ cellular” about a moner or a blood-corpuscle. The name was 
given when the nature of these protoplasm-masses was misun- 
derstood. From the fact that in some tissues they secrete around 
themselves a membranous envelope, it was inferred that all did, 
even where such structures could not be demonstrated. This 
real or supposed envelope was then considered not only an 
essential, but the most essential feature of the. elementary part, 
and therefore the whole was not unnaturally called a cell. From 
being in such common use, and being also a short convenient 
word, the name “cell” has been retained, but I beg you to 
remember that in its present employment it is only a name, and 
not a descriptive appellation. 
With respect, finally, to the methods by which protoplasm 
performs the fundamental vital acts, I need not recapitulate 
what has been so often described already. I will only in this 
connection point out to you the important fact that so far as 
observation has yet gone—mark the proviso—protoplasm has 
never been definitely known to arise de novo, but is always 
found derived from pre-existing protoplasm by bodily division 
of one unit-mass into new individuals or germs. 
Such, then, are the pregnant facts that the microscope has re- 
vealed, and I leave you to judge whether I was justified in say- 
ing at the beginning of the lecture that st common denominator 
of life had been found. You have seen that throughout the vast 
domain of the animate world, from man to the monera, there 
is but one kind of actively living matter—protoplasm : but one 
mode of its existence, in elementary unit-masses: but one scheme 
of tissue-building, the nmImplication and transformation of such 
elements: and apparently but one mode of continuance of life 
on earth, direct division of protoplasm-units into new genera- 
tions of the same. 
Of the significance of these facts and their bearing upon the 22 
great moot questions of science and philosophy, I no time 
to speak. That they are of deepest import, I need not tell you: 
it is plain to the most careless thinker. They must enter as a 
necessary factor into every hypothesis of the origin and mutual 
relationship of living things, or of the nature of life and the 
so-called vital force. Even the question of our own proud 
position among earth’s creatures must be argued by the light of 
the facts concerning protoplasm. For man himself does not 
escape the community of matter and manner of life that links 
into one chain all animate forms ; and more startling even than 
our likeness to the ape is the thought that at the beginning of 
our individual life, as the fecundated egg, we, the highest of 
created beings, are but a compeer of the lowest: man and 
moner brother-forms after the same simple type—twin unit- 
masses of a universal living matter! 
But there are yet deeper secrets hidden in nature’s bosom 
than what you have learned to-night: and as one object of my 
lecture was to illustrate the method of investigation in natural 
science, I cannot close without a warning word as to some of 
the requirements of that method, which, unfortunately, are but 
too often disregarded. The sailor who knows beforehand the 
position of the harbor he seeks, can by chart and instru- 
ments lay his course and sail it with unfailing certainty. But 
to the hound that hunts the stag through the forest no forecast- 
ing of his route is possible. lie must be content with the tedi- 
ous method of striking the trail of his prey, and following 
blindly all its devious windings. Yet is this faithful tracking 
of the hound as unerring as the compass of the mariner, for the 
one will run his game to earth as surely as the other makes his 
port. 
Now we who seek after the great unknown, the secrets of 
nature, are as the hound in the chase. Like him, we know not 
where in the forest before ns the game lies hid, and our only 
course is his. We must search for footprints, and having 
found them, patiently and determinedly follow their leading to 
the end. To do so, we need keen eyes and clear heads, for the 
tracks are often faint, and the trail winds and doubles on itself, 
and is crossed by many an alluring false scent. But above all, 23 
we must, at the outset, abandon every preconceived idea of the 
position of our chase, and, recking not whither we go, follow 
faithfully the winding trail, confident that though it may lead 
through tangled jungles or over dizzy heights, it cannot, in the 
end, but guide us aright. In Dante we read over the gloomy 
portal of Hell, “ Leave Hope behind all ye who enter here ” ; 
but over the beautiful broad face of Nature, there is written on 
every stone and leaf—murmured by every brook—warbled by 
every bird, the warning that I bid you heed:—Who cometh 
here to learn, leave Prejudice behind.