A DISSERTATION ON "THE CELL DOCTRINE."

BY HENRY HERBERT EDWARDS, D.D.S.

Read before The Alumni Association of the Philadelphia Dental College, Feb. 28, 1883,

What is a cell?

Simple as the question appears, what a volume of thought is required in order to answer it intelligently from the physiological standpoint.

Since the time of Aristotle, 384 B. C., down even to the present day, it has proven a pit-fall to all the scientific researches made by philosophers, physiologists, materialists, or by whatever name language has endowed those men of mighty brainpower-who have essayed to fathom the inscrutable.

Exception may, and possibly will, be taken to the foregoing remark, by bringing forward the numerous and varied theories, which from time to time have been propounded; conclusive theories, illustrating the abilities of each succeeding era. The latest description of a cell is, without doubt, the best that has ever been given, namely, "The smallest portion of organism possessing essential properties for nutrition, development, growth, maintainance and reproduction." True, but nevertheless vauge; for it carries with it no definite meaning.

The physiologists are deserving of great praise for the thorough manner in which they have done their work of love, in discovering and explaining the functions of the nucleus and nucleolus, still there is a something that cannot, or at all events has not been fathomed: what is beyond?

Let us follow, for a moment, a history of their researches, for that alone is interesting. In the first place magnifying glasses of a single lens, were known as early as 500 B. C., and although it was then thought that the human body was composed of minute particles, yet there

were no means of proving the fact, it not being until the year 1590 A. D. that the compound microscope was invented, which discovery was due to the Jansens-father and son. Two thousand years of ignorance, in spite of possessing magnifying glasses!

Again, it was not until nearly one hundred years after the use of the compound microscope was made known, that Borellus, of Pisa, in the year 1656, by the use of that instrument, discovered corpuscles in the human body.

The results of his investigations may be likened to the first bright streak of dawn piercing the black night-clouds of ignorance or indifference, and compelling them to roll back before the light and splendor of advancing knowledge.

Emulating his masters glorious achievements, Malpighi, in 1661, demonstrated the existence of corpuscles in the hedgehog. It is good to dwell for a moment upon the thought that these two men, master and disciple, were the cornerstones upon which has been built that mighty fabric called "The Cell Doc

trine."

These discoveries were quickly followed by those of Leenwenhock, in 1673, who demonstrated the presence of cells or corpuscles in man; and he affirmed that "the cell-wall stretched with the growth of its contents, which act was clearly the result of vital phenomena ;" also, "the governing force that presided over and ruled the development of cells seemed to determine them into the different tissues of the body."

Another cessation in the growth of this great study; for there is nothing of importance recorded until the year 1805, when Oken taught that animals and plants were made up of nothing else than repeating vessicles, globules, circular bodies, or granules, having no fixed size or shape.

Hensinger and Heale, 1822-4, discovered, by careful watching, that the

cells overlapped each other, and, by absorption of the central portions, they formed tubes or vessels, and if absorption did not take place they made fibres. Up to this date no mention was made of a nucleus; its discovery, in 1833, is due to the praiseworthy labors of Dr. R. Brown, of Edinburg. The nucleus he believed to be the living matter which produced the increase in size of the surrounding cells, and consequently of the tissues they being made up of cells.

In 1838, Schleiden and Schwan demonstrated that animals and plants were built up entirely of globules, and pronounced their theory of cell-budding, i. e. the nucleus and cell-contents contracting in the centre, dividing into two, and growing only to be again subdivided to infinety.

Professor Huxley, in 1853, defined the nucleus as the "endoblast," and considered it was not so important as the "periblast" (the cell-wall and contents).

The various schools of physiologists seemed to differ a great deal as to the proper name with which to endow this piece of protoplasm, for we find it called a cell, vessicle, globule, granule, spherical-body, protoplasm, bioplasm, surcode, etc. Dr. Bennett, in 1855, described the nucleus as "the ultimate part of living matter," and he experimented with clear animal effusion and watched the cells form into fibres.

The next worker in this great field of thought was Virchow,who shaped the study of physiology more than any of his predecessors. He propounded the theory of "Omni cellula a cellula," and spoke of a nucleus, cell-wall, and cell-contents as being necessary to a cell; but later on he gave up the idea of a cell-wall, though the theory of a nucleus and cell-contents he retained until the day of his death.

The nucleus, he considered to be the life, the reproductive element, or at all events, the place where life resided. He further stated that if the nucleus was

healthy, its proginy were also healthy, and vice-versa; upon that hypothesis he built his theory of " Cellular Pathology," which is to-day regarded as the basis for the study of all disease.

In 1861, Max Schultze, described the cell as a living, moving, constructing substance, having an outside or cortical layer, within which was a fluid and proto. plasm. Lydig taught that the life of a cell was an independent one; the death of one not producing the death of all.

E. Brûcki founded a school which held the views of "Dispensing with a nucleus," for he discovered certain plants, the cells of which had no nuclei.

Stricker found the same results experimenting with the eggs of a frog. Max Schultze exhibited amabi without cellwalls or nuclei.

Çienowski, likewise brought to light monads without nuclei.

Science is indebted to Dr. Lionel S. Beale, for quite a "new departure" in regard to theories, and one that certainly is to be accepted, if alone for the sake of doing away with conflicting terms. He divided the cell into two portions, namely, "germinal matter" and "formed material;" the germinal matter possessing the power of developing pabulum into living organism, and the formed material made by the death, or partial death, of the germinal matter, being ready to perform the functions expected of it by the body. The germinal matter, he describes as a soft, translucid, colorless, structureless, active, living, growing and moving miss, which, as it advanced, left behind a trail of formed material; which formed material is a passive, non-acting substance, although capable of being acted upon.

The cells, he says, grow from within outwards; the inner being the younger portion of the germinal matter, and the outer, the older portion, changing by its death (being cut off from its supply of pabalum) into the formed material.

Having thus briefly scanned the various theories, we will add some of the latest teachings and then draw our own conclusions.

One of the most general forms of an "elementary part" is that which is commonly known as a cell. This in its complete and characteristic form, consists of a definite cell-wall, enclosing cell-contents; and the latter, whatever may be their special nature, include a nucleus, which has long been regarded as specially related to the formative activity of the cell. But there are many objections to this use of the term "cell" as indicating the elementary unit of structure. are a large number of cases in which there is no more definite investing membrane than there is in the body of an amæba; the "elementary part" being entirely composed of a mass of protoplasm or "germinal matter," of which the exterior has undergone a slight consolidation, like that which constitutes the primordial utricle of the vegetable cell.

There

This is the case, for example, with the colorless corpuscles of the blood, with granulation cells and pus-corpuscles, with the corpuscles of the ductless glands, and with cells generally in an early stage of their development; the layer of “formed material" being here very thin, and its separation from the "germinal matter being far from complete. In a more advanced condition, we find the "germinal matter" limited to a smaller proportion of the interior of the cell, so as to constitute what is known as its "nucleus," and this is surrounded by more differentiated "formed material" which may still have no definate investment. Such appears to be the case with the red corpuscles of the blood of Oviparous Vertebrata, for although these are commonly described as perfect "cells" having a cell-wall that contains the colored substance, no such cell-wall can be demonstrated, and the changes of form

which these corpuscles can be made to undergo seem to disprove its existence.

Again, in cartilage we have an example in which the nucleus and cell contents are completely differentiated from the cellwall, but the cell-wall itself cannot be separated from what has been distinguished as the "intercellular substance," which is commonly regarded as the "matrix" wherein the true cartilage cells are imbedded; and it would appear from a study of the history of its development, that the "intercellular substance," "cell-walls" and "cell contents," are all to be regarded in the light of layers of "formed material," successively exuded from the mass of "germinal matter" in which the cell originated; this, on the other hand, contracting until it remains only as the "nucleus." The most characteristic examples of fully formed and independent cells are presented to us in Fat-cells and Epithelium-cells, for here we have a definite limitary membrane, distinct alike from the contents of the cell and from the matrix in which the cell is imbedded, whilst the cavity of the cell is occupied by some product that has been elaborated by the agency of its mass of "germinal matter," which may remain to constitute its nucleus, or, in cells that have entirely ceased to participate in any active change, may entirely disappear.

The difficulty of all research may readily be conceived when we consider that the smallest portion of protoplasm demonstrated is but the .00001 of an inch in diameter.

A cell, then, in the language of physiology, is a closed vessel or minute bag formed by a membrane in which no definiate structure can be discerned, and having a cavity which may contain matters of variable consistence; but which possesses in itself the power of growth and (in its typical condition at least) of multiplication also. In such a cell, every organized fabric, however, complex originates.

The various forms of cells are as fol

lows:-Spherical, oval, polyginal, hexagonal, squamous, tesselated, columnar, cilliated, unipolar, bipolar, multipolar, spindle-shaped, tadpole-like, and stillate, all of which are found in various parts of the body.

Every kind of cell has its own specific endowments; and generates in its interior a compound peculiar to itself. The nature of this compound is much less dependent upon the nutriment materials which are supplied to the cell, than upon the original inherent powers of the cell itself, derived from its germ. This substance was termed sarcode" by M. Dajardin, who first drew attention to its peculiar nature as exhibited in animalcules etc. Among those who have studied its characters in the higher animals it is commonly known as blastema or "formative material," while Dr. Beale, who has greatly extended our knowledge of its endowments and of funḍimental importance in operations of nutrition, has designated it by the term "germinal

matter."

In the young cell the germinal matter preponderates, but as the age of the cell advances, opposite results take place, the germinal matter aiding its own death by shutting itself completely off from its supply of pabulum, in its laudable efforts to supply the tissues with formed material giving, thereby, to the moralist a splendid example of self-sacrifice in the performance of duty.

Cell formation resembles the three epochs of life-infancy, manhood, old age,-once strong, twice weak.

The germinal matter assimulates to itself from the blood, as much pabulum as it requires, the pabulum passing in through the formed material by means of minute vessels. If the germinal matter assimulates an excess of pabulum, hypertrophy is the result; on the other hand, a deficiency of pabulum. constitutes atrophy of the cell, and dimin

ution in the member of cells causes atrophy of the tissues.

Science has not yet determined what that substance or fluid is that lies between and surrounds the cell; it may be pabulum or the fluid in which the cell is nourished, or it may be an oozing out of something from the cells; whatever it be, it is said to contain water and certain gases.

A deficiency of pabulum may bring about a pathological condition of the cells, and diseases may be communicated from one kind of cell to its fellows by means of connecting filaments.

The cell-wall (if that theory be accepted) is composed of either albumen or one of its derivatives; it is with regard to the nature of the contents that the greatest diversity of opinion exists.

Theoretically we are taught of hereditary transmission of impressions, and it certainly seems possible; when we consider that, according to Harvey, “Omni vivam ex ovo.' Memory certainly must be due to the handing down from one cell to its offspring, the received impressions; also in cases of hereditary diseases, it seems conclusive that the sperm-cell should contain granules of such disease.

We learn that in sickness a great mass of germinal matter dies, and if there be not sufficient pabulum in the blood to construct new cells, to replace the wear and tear, physiological waste of the tissues ensues and death is the result.

The animal cell is in all essentiul particulars the same as that of the vegetable, with this exception-that the animal cell derives its nutriment from organic compounds, previously elaborated, instead of generating them, like the plant, at the expense of inorganic elements. It lives for itself and by itself; being dependent upon nothing but a due supply of aliment and heat, for the continuance of its growth, and the due performance of all functions until its term of life be expired. In whatever method it originates, it at

tracts to itself, assimulates and organizes the particles of the nutrient fluid in its neighborhood, in this manner gradually increasing in size, and whilst approaching the term of its life, it may make preparations for the development of reproductive particles in its interior, which may give origin to new cells when set free from the cavity of their parent.

Thus then we see that our fundin.ental

idea of the properties of the simplest living matter consists in this,—that it has the capability of drawing into its own substance certain of the elements furnished by the inorganic world, - that it forms these into new combinations,that it re-arranges the particles of these combinations in that peculiar mode which we call "organization,"-that in producing this new arrangement it renders them capable of exhibiting a new set of properties which we call "vital," and which are manifested by them either as connected with the present organism, or as appertaining to the germs of new structures, according to the mode in which the materials are applied, -that notwithstanding its peculiar condition, it remains subject to the ordinary laws of chemistry, and that decomposition of its structure is continually taking place; and finally, that the duration of its vital activity is limited, the changes which the organic structure undergoes in exhibiting its peculiar actions, being such as to render it (after a longer or shorter continuance of them) incapable of any longer performing them.

More, much more, could be said on this grand subject, but we must abstain and bid it adieu, with one closing thought.

One cannot pursue science without acknowledging a great first cause-a God. Huxley, who, however, is no atheist, says that " even the thoughts to which we give utterence are the result of molecular motion." We are glad that we are taught not to accept that statement, for we are bound to admit that behind all there is a

something that cannot be explained--the Soul of man. That is the terra incognita" of scientists; and when Huxley claims that his statement is true, he also adds that he considers materialism involves grave physological errors. We can only go so far as to say that the intelligence, ghost, or life of the cell seems to reside in the germinal matter, for if that dies, there is an end to the existence of the cell; and that the germinal spot is formed of a certain material, endowed by a Supreme Power with singular properties that develope the capital cell into whatever it is destined to be.

To conclude, then, we only know of life, as exhibited by an organized structure, when subjected to the operation of certain "forces" which call it into activity; and we only see vitality or the state or endowment of the being which exhibits that action as conjoined with that particular aggregation and composition which we term "organization."

Therefore, if we endeavor to assign a cause for the existence of a cell germ, we are led at first to fix upon the vital operations of the parental organism by which it was produced and for these we can assign no other cause than the peculiar endowments of its original germ, brought into activity by the forces which have operated upon it. Thus we are obliged to go backward in idea from one generation to another; and when at last brought to a stand by the origin of the race, we are obliged to rest in the Divine Will as the source of those wonderful properties by which the first germ developed the first organism of that race from materials previously unorganized; this organism producing a second germ, the second germ a second organism, and so on without limit, by the uniform repetition of the same processes. Yet we are not to suppose that the continuation of the race is really in any way less dependent upon the will of the Creator than the origin of it.