On Protoplasm

338 Reviews. [April,

V.?On Protoplasm.1 No one can, -we tliink, mistake the tendency of modern biology; whenever it is possible, and sometimes when it is hardly possible as yet, rule and measure are called in to give exactness of expression to our knowledge of the subject, and exact data are formulated in terms of mathematical precision. Improved chemical processes are gradually enabling us to resolve those " waste heaps or dust bins labelled extractive matters" into their components; and many phenomena which, not under- standing, we used to term vital, have been found after all to be readily intelligible on the ordinary principles of chemistry or physics. So many things heretofore supposed to depend directly on the vital principle have been thus resolved that some have gone so far as to call in question the existence of any force different from the physical forces we sec at work around us. Undoubtedly the discovery of the correlation of these forces, the fact that one is transmutable into another without diminution and without increase, has had a most important bearing on physiological doctrines. If in the physical world we see motion transformed into heat, this into light and chemical action, chemical force into electricity and magnetism, and so on, we are tempted to make another step in advance. In vegetable life we know that light and heat are the forces whereby carbon is fixed and oxygen set free, whereby ammonia is converted into com- plex organic compounds, and an infinite variety of other changes is effected. In animals it has been found that digestion is a chemical process, absorption to a great extent a physical one; respiration is partly physical, partly chemical; not a muscular movement can be performed without the consumption of fuel in some shape or other; in short, in all these so called vital acts the physical forces are equally manifest as if there were no com- plex organic medium through which to exert their influence. The question therefore arises, Suppose we take the simplest

" i 1. The Fortnightly Review (February 1st, 1869). On the Physical Basis of Life. By Professor Huxley. London. 2. Protoplasm or Life, Force and Matter. By Lionel S. Beale, M.B., F.R.S., Fellow of the Royal College of Physicians, Physician to King's College Hospital. Second Edition. London. in relation to on 3. -As regards Protoplasm Professor Huxley's' Fssay the James Physical Basis of Life. By Hutchison Stieling, F.U.C.S., LL.D. Edin. Edinburgh. Gilbert W. 4. on Physiological Subjects. By Child, M.A., F.L.S., &c., Essays London. Lecturer on Botany at St. George's Hospital. and Present the Use in 5. The Cell Doctrine, its History State, for of Students Medicine and Dentistry. By James Tyson, M.D., Lecturcr on Microscopy in the University of Pennsylvania, &c. Philadelphia. 1872.] On Protoplasm. 339

organism known, and consider well its functions, is there any- thing in these not explicable by physical force; shall we be forccd to call in some mysterious entity of which we know nothing, to explain the terms of its being? If we let fall a drop of white of egg yet unboiled, into water, this drop retaining its individuality and mixing not with the water, represents the simplest organised, or rather we might say unorganised, being. Haeckel calls it monerci, but herein consists the difference: this monera having 110 other structure than a drop of albumen, can move from place to place of its own accord, can change its shape in a thousand ways, can take in and make part and parcel of itself other and larger portions of albuminous matter, and can reproduce itself by throwing off a portion of its own substance, and all this it does by virtue of something we call life. But it has been roundly asserted that this property is in- in kind of matter we are now herent the with which dealing ; ?where it exists life exists, and where it does not exist no life is, insomuch that it has been called the physical basis of life ; let us call it protoplasm. The questions in dispute seem to formulate themselves thus :? Does the existence of protoplasm, using the word in a strict sense, imply life; may life and matter co-cxist whilst the latter assumes 110 distinctive form ; can life begin da novo and without the agency of pre-existing life ? But to the preliminary inquiry of what is protoplasm ? using the word-in the strict sense, we obtain 110 adequate reply. We are told that all forms of it contain carbon, hydrogen, nitrogen, and oxygen in certain proportions, but what these are we know not. Protoplasm, in a strict sense, is not known chemically. If we seek for an example of protoplasm, we are referred to the well-known experiment with frog's blood. A drop is drawn from a blood-vessel of the animal and deposited 011 a piece of thin glass; this is placed under the microscope,and kept at a temperature of about 100? F., when by-and-by the white corpuscles will be seen to approach the edge of the blood drop, exhibiting distinct movements of the kind called amoeboid. Similar bodies are found in connective tissues, some wandering, some fixed, but apparently otherwise identical. To these we are referred as samples of protoplasm, but we are ignorant as ever of its chemical even indeed, this would seem to be far from simple composition; would in in fact the type of bodies leucocytes; protoplasmic of fat appear to have at all times during life a certain proportion combined with its albuminous matter, the sepaiation intimately of the death of these two constituents being the first certain sign forms of of the body. Professor Huxley tells us that all the pro- 340 Reviews. [April,

toplasm yet examined behave similarly towards several reagents ; if this be true of protoplasm, it is certainly not true of the type of such bodies, albumen itself; for this sometimes will coagulate with acid, and sometimes will not; sometimes too it will coagulate with heat, and sometimes it will not. Syntonin, globulin, and peptone are all varieties of albumen ; of all may different characters be predicated, but of none can it be said that it is the matter of life or protoplasm. Nay, if we fall back on what we are told is the type of protoplasmic structure, a white blood-corpuscle or an amoeba, we find in its body certain portions apparently constituted differently from the rest, inasmuch as by a reagent such as acetic acid we can demonstrate the existence of particles called nuclei, which behave differently from the rest of the structure. The same is the case if the body be killed by an electric shock, without any chemical reaction. It is, however, perfectly true that in monera there is no nucleus, which shows that this is not quite essential to the performance of all the acts of life, but it is also quite true that in those bodies possessing a nucleus, changes in it generally precede changes in the mass of the being itself. If possible, this nucleus shows a more vigorous vitality; is it protoplasm ? If so, it reacts differently from the rest of the mass. If, therefore, we mean by protoplasm merely the simplest form of living matter, that is, if we make vitality the test of its existence, we can understand the meaning of the word. But it is plain that protoplasm is not a simple substance in all instances chemically identical; in this sense it is a varying admixture of more than one body of albuminoid constitution, reacting differently with different reagents. Its presence is not the test of life, but life of its presence. Professor Huxley himself hints at these differences of properties when he speaks of the difficult digestibility of lobster protoplasms as compared with that of sheep; in other words, these two do not behave exactly in the same way towards the reagent we call gastric juice. There is, however, one sense in which we may make use of the word protoplasm with advantage; to illustrate this we must fall back on matters of history. When Schlciden had shown that the plant was built up of a scries of elements, as a house is of bricks, he investigated the structure of these elements, and found that in every instance they seemed to possess a cellular wall, slimy contents, and a nucleus, besides other things, as starch, chlorophyll, and such like. Schwann adapted these principles to the human body, and applied the term cell, introduced by Schleiden, to designate these ultimate vegetable elements, to designate also those of the human frame. Further- more, a similar constitution was predicated of them; that they 1872.] On Protoplasm. 341 consisted of cell walls, slimy contents, and nucleus; in short, that they were in every way analogous to the vegetable cells. But in 1835 Dujardin, then concerned in his inquiries into the Hhizopoda, discovered that they consisted of a substance irritable and contractile, having nothing of a cellular character; it was called sarcode. llesearches went on, and new discoveries were that made, especially the slimy substance of many animal cells was also contractile, until at last Max Schultze was able to show the that contents of animal cells were analogous to sarcode, and that the cell Avails were of comparatively little consequence compared with their contents. In the days when this universal character was predicated of all animal structures, blood corpuscles, red and white, were a standing difficulty; by no means could the red globules be reduced to the highest or nucleated ccll type, and by many they were held to be free nuclei. White corpuscles were more easily managed, for by means of reagents something like a ccll wall and multiple nuclei could be made out. But when these last named bodies had been better studied, and their curious movements, exactly resembling those of a protist, bccamc known, their analogy to a mass of sarcode was recognised, and it was admitted that a wall was no longer to be held as an essential portion of an animal cell. This new advance may be said to have been made simultaneously by Max Schultze and Lionel Beale. These two observers, however, looked at the matter from different points of view. Schultze considered chiefly the irritability of the cell contents, to which he gave the name of protoplasm, whilst Beale, looking rather at one definite chemical reaction, considered all material readily tinged by carmine solution as germinal matter, and that not so affected as dead or formed material. The selection of these terms seems to have been peculiarly unfortunate; they have never been generally accepted, nor, perhaps, even understood, and their use, in a fashion to many unintelligible, has done much to deprive Beale of that reputation most justly his due, and to cause to be assigned to German discovery that which had long before been done among ourselves. At all events, the results of Schultze's investigations entailed the rejection of the cell wall as an essential portion of the animal cell, which he considered to be made up of a particle of protoplasm and a central nucleus, sometimes having the outer portion of the protoplasm condensed modified so as to constitute a kind of membranous wall, or even a true wall. into a substance not protoplasm, and constituting " " But," said he, in fact, a cell with a membrane chemically different from is comparable to an encysted mfusory. protoplasm denied Nor did matters halt here. Briicke went further, and the he based his necessity of a nucleus in the ideal animal cell; 342 Reviews. [April,

mainly on the cells of certain cryptogams in which no objections " nucleus was known. "And," he argued, as there is nothing known either of the constant presence of the nucleus or of its functions when present, why should Ave include it in our con-" ception of Avhat is essential to a living portion of animal matter, commonly called an animal cell?" This notion as to the non-essential character of the nucleus was speedily confirmed by the discovery in the Adriatic of an amoeba (A. porrecta), by Max Schultze, devoid of nucleus; this again was followed by the discovery in the Mediterranean of Protogenes primordialis, a larger form, also non-nuclear, by Haeckel. Other kindred organisms were found by Cienkowsky, and, finally, Haeckel found in the Canary Islands that struc- tureless protist he has so well described in his monograph as Monera. This irritable and contractile substance then, the sarcode of Dujardin, the protoplasm of Max Schultze, the germinal matter or bioplasm of Beale, so constituted as to be able under appropriate circumstances to maintain an independent existence, yet corresponding with the active material inside true cells, may be spoken of and considered histologically as protoplasm. Chemically, it agrees with a whole group of protein or albuminoid bodies. If, therefore, we use the word protoplasm chemically as synonymous with protein or albuminoid substance, it is nothing new, and we are certain that it is not, in the meantime, capable of a more exact definition by chemistry. Of all chemical substances, perhaps protagon most closely approximates to what is called protoplasm in character, but neither of that, even although it tends to assume shapes resembling cells, can it be said that it is protoplasm. But though incapable of this close and exact definition, the term is nevertheless a very useful one. It expresses the idea which it is so desirable to bring out, that between animal and vegetable matter there is no great gulf fixed. It is known that certain forms of life are at one time similar to vegetable, and at another period of life history more like unto animal organisms ; it is well then that there should be a common title for the substance, which may thus be impressed with either an animal or a vegetable character, but which in essentials remains the same. There is yet another way in which the term is valuable. It is e plain the term cell' as applied to a body possessing the characters of a leucocyte, whether wandering or fixed, is a misnomer, and yet a very considerable number of what are now frequently called elements are constructed on this type. For these it is desirable that the term cell should be abandoned, and though the substitution of protoplasmic mass for cell may be the sub- 1872.] On Protoplasm. 343

stitution of a long term for a short one, it lias the merit of con- veying no false impression. As already pointed out, the characters of such a protoplasmic mass as monera or a white blood-corpuscle are irritability, con- tractility implying the power of changing shape and station, nutrition and reproduction. But apart from these characters, protoplasm may be active, resting, or dead. By irritability we merely imply the possibility of the powers of a protoplasmic mass being called into play by some agent external to itself, and of these the simplest and most efficient is heat. If we take a portion of the leaf of an Anacharis alsin- astrum, now so common, or of a Vallisneria, surround it with a drop of water, and cover it lightly with a thin piece of glass, we may, if the temperature be rather low, see nothing save the cellulose compartments dividing the cells one from another, and the cell contents containing abundance of chlorophyll granules; but if we use a lamp for our illuminating agent, its rays of heat are reflected 011 to the leaf as well as its light-giving rays, so that presently we see active motion of the cell contents, as indicated by motion of the chlorophyll granules, set up in every direction. Here is the stimulus of heat setting up motion in the previously resting protoplasm. This is still better exemplified by the behaviour of the leucocytes contained in the circulating blood of a triton or sala- mander. The experiment is easily made by any one who can command the means of warming the stage of a microscope, and for this no elaborate apparatus is needed. Care must also be taken that the drop of blood does not dry, so it must be placed in a cell and surrounded by vapour. When withdrawn from the veins of the animal, the white corpuscles are seen as rounded, well defined masses, presenting a marked contrast to the elliptical corpuscles of the red kind. This is the resting condition when no particular stimulus is acting upon them. For as the observer watches these rounded bodies change their shape, they probably become elongated and more transparent; presently their edges become jagged, and a scries of active changes of shape ensue. These changes become more active up to a temperature, a few degrees above a hundred, but if this limit be transgressed their motion ceases,and in 110 wise can it be made to begin again; the leucocyte is dead. But apparently intermediate between the conditions of active life and motion, and irretrievable death there is the is not clear. condition of rest, whether of repose or tension quite the blood At all events, this can be done; leucocytes of can, by electric stimuli, be made to gather together into a clump, been too which after a time, if the stimulus has not strong, 344 Reviews. [April, gradually resumes the mobile condition. But with the protoplasm of a cartilage-corpuscle this is not possible; contraction of the protoplasmic mass on its nucleus may be easily brought about, but no further change results; it is dead. Nevertheless, we have no reason to believe that the electric stimulus has in any way altered the chemical properties of the substance; it will imbibe carmine as readily as ever. Yet though the protoplasm is there, life has departed. The existence of protoplasm cannot be said, therefore, to predicate even the potential presence of life. Nay, more, protoplasm as studied in the living body presents different degrees of vitality. The connective-tissue corpuscles, of which one has heard so much, seem to be of two kinds, some fixed like the corneal corpuscles, which give out processes in various directions, some like the cartilage-corpuscles, resembling in outline a resting leucocyte, but not possessing, as pointed out above, the same degree of inherent vitality. Others again are found in various tissues, emigrants from the blood vessels, though now in a condition of rest, whilst the most active members of the class seem to be the leucocytes of blood and lymph. These, as we have seen, readily respond to stimuli; they also grow, as we infer from their presence, in very various sizes in the interior of the vessels, and they are capable of reproduction by fission, in all probability within the vessels and glands, certainly outside them, when they have wandered into the surrounding tissues. It is very strange that doubts as to the truth of the phenomena we have referred to should still exist in the minds of many when they are so readily capable of proof. The changes in the corneal corpuscles of the frog after irritation as by nitrate of silver, are easily studied, especially by the method of staining with chloride of gold, now in vogue. The migration of white blood-corpuscles may now be studied by any one who can command a tolerable microscope, and can get hold of a frog. By all these phenomena we are impressed with the truth of that view which teaches that it is the living matter of the so-called cell which is of importance; its outward configuration or its envelope matters little. It is absolutely necessary to have a name for this irritable and contractile substance, and we know of none better than protoplasm; but protoplasm may be alive or it may be dead; in the latter state it is neither irritable nor contractile. It is clear, therefore, that the presence of life implies no specific form, neither does the existence of protoplasm imply is the presence of life (its pre-existence another question). The final question arises, May life begin de novo without the agency of pre-existing life? To this, after due consideration, we are bound to reply, No, not as far as our knowledge goes. It would 1872.] On Protoplasm. 345

be beside tlie purpose to argue the question whether dead protoplasm can come to life again under the influence of the simple forces heat, light, &c., because until we can manufacture protoplasm it is not possible to sav that we do really begin de novo. And yet this is the only form of the question which admits of argument. We know of no chemical means whereby the simple elements already alluded to oxygen, hydrogen, nitrogen, and carbon, Avith sulphur and phosphorus, can be combined so as to resemble living matter, or the matter of living beings. And the idea that living beings can be formed from matter which does not contain all, or at all events four of these elements, may be surely put on one side, so that any admixture of compounds of these not containing all of them cannot by any possibility be converted into a living being. The argument as to whether dead protoplasm can come to life again is a vain one until botli parties can agree upon a distinct boundary line between life and death, and on an unfailing test for matter in either state; an agreement which we need hardly say does not exist at the present day. To our minds reasoning from analogy has always seemed a powerful weapon if used aright, and in the present inquiry it cannot be denied that the analogy is entirely on one side. If we trace the history of the simplest protoplasmic masses, they begin as exceedingly small offshoots from a parent like themselves. As we see them in the animal body, they are surrounded by food, and rapidly grow. Yea, leucocytes as they exist in living animals can be fed on special substances. In the frog white corpuscles often devour portions of red ones. If aniline blue is introduced into a lymph sac the leucocytes ingest the blue particles, which may be seen in their interior as chlorophyll is seen in the protoplasm of a vegetable cell. The same occurs if they are fed with carmine, and so these corpuscles may be traced throughout the body. In inflammation such marked bodies are seen rapidly dividing and rapidly growing. Even in the living body we have every reason to believe that the doctrine omnis cellula e cellula is true when cellula means a mass of protoplasm. Outside the body the rule is the same; when animals are unicellular, their history is like that of a leucocyte the inside an animal. The more plentiful their food, the greater heat within the limits already pointed out, the more do they on the multiply and increase, and if any one reflects rapidity he can Avith which an abscess forms within the organism be observed readily understand that a similar rapidity may that a outside it. But this, is to be borne in mind high again, well known temperature is not absolute, but relative, as in the instance of the ova of certain fishes [ex. gr. the trout), which 346 Reviews. [April,

proliferate rapidly at a temperature which would kill many forms of animal life, and which would themselves be destroyed by a greater lieat. Omne vivum e vivo is, as far as we know, the rule. That there seem to be exceptions every one admits; that these exceptions are real and not apparent only is another thing. In dealing with the history of protoplasmic masses we found that though it was easy to tell the active from the resting form of a leucocyte, it was by no means easy to tell the resting form from the dead condition save by the separation of fat and gradually advancing decay. Experience with regard to infusories teaches that in them the distinction is, if possible, harder, and by the distribution of such protoplasmic masses in a resting state doubtless many of the instances of so-called heterogeny may be explained. With experiments like those of Pasteur, on the one hand, and those of Pouchet, Bastian, and others, on the other, a hasty judgment would be the acme of rashness. Nevertheless, the one view has the analogy of all animated life to support it, the other merely the care of the ex- perimenters or their reputation for care; and on them, too, lies the onus probandi. We can only hope that in due time their care will be rewarded, and truth, the object of them all, attained. Finally, the active and the resting conditions of protoplasm are, to the medical world, of the very utmost importance. The two conditions explain much with regard to the spread of epi- demic and contagious disease, without calling in the aid of any mysterious bodies, germs or otherwise. They encourage the use of antiseptics or bodies capable of unmistakably killing protoplasmic particles, be they what they may. And as the size of a particle of protoplasm which may rest for a time, and again, with favourable conditions resume activity is unknown, but is in all probability infinitely small, they suggest the utmost care in the destruction of these.