Biology, general and medical

Front matter

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Med

I

Preface

In preparing this book it has been the purpose of the author to acquaint his readers with the peculiar nature and interesting reactions of “Living Substance’’ ; to help him trace it to its probable, though unknown, beginnings and follow it through its multifarious differentiations to its highest complexity.

In so far as this has been accomplished, the work is a General Biology. But more has been attempted, for the problems have been so considered as to show that man is no separate entity, apart from the general world of living things, but is a unit in the general scheme of things and subject to the same laws that apply throughout the universe.

Inasmuch as many of the subjects treated are of importance to students contemplating future medical studies, and inasmuch as all of them are of interest and importance to students of medicine and physicians, the work may, with justification, claim to be a Medical Biology.

All of the problems of medical science are in a sense biological, and many of the problems of biological science medical. Medical science is, in fact, a branch of biology and should be studied as such.

Each chapter treats of some subject or subjects upon which the pen would gladly linger and upon which a volume might be written, and professional biologists will, no doubt, be disappointed at the brief treatment their pet theories receive as well as astonished at the space devoted to other, and to them less important,

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PREFACE.

matters, but this is the inevitable result of the particular point of view of the author.

Nearly all of the subjects treated are of controversial nature, but that is the present state of biological science. Attempts to crystallize incomplete information into laws lead to theory rather than to fact, and the subject passes from theory to theory in search of the fact. This explains why the consideration of certain subjects may lead the reader to a final interrogation point or may end without a personal expression by the author in favor of one or the other side of the question.

It is hoped that the problems of Blood-relationship, Infection, Immunity, Parasitism, Inheritance, Mutilation, Regeneration, Grafting, and Senescence, which have been presented at greater length than in other writings upon Biology, may be useful to the reader.

It is hoped that the writing will not be found too technical to be beyond the comprehension of any intelligent reader, though it must be admitted that some acquaintance with the sciences will be of decided advantage to him.

The author expresses his sincere thanks to his friend and colleague, Professor Charles H. Shaw, A.M., Ph.D., for many valuable suggestions and criticisms.

Philadelphia, Pa., JOSEPH McFARLAND.

September, 1910.

Chapter I. The Cosmical Relations Of Living

MATTER.

To study the problems of life apart from their cosmical relations is to lose much of their significance. It is only by an appreciation of the endless changes — integrations and disintegrations — that pervade the universe that one comes to realize that those qualities by which we recognize living substance more or less closely correspond to the qualities of all substance, and those forces by which it is animated to those forces by which the universe itself is controlled.

All the demonstrations of physics arrive at one conclusion: that the universe consists of matter that is indestructible, controlled by forces that are persistent. Beyond this it is not in the power of the human intellect to penetrate.

We know nothing and probably never can know anything of the origin of matter or force, and are obliged to content ourselves, as our antecedents have done, with the knowledge that both exist, and that we can only recognize the existence of force as it influences matter, and only know matter as it is affected by force.

The planet upon which we live consists of matter in a highly differentiated state which the chemists are able to resolve into a certain number of forms so stable as not to be susceptible of further analysis, and therefore called

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“elements” Astronomy, however, shows us that the primitive form of matter is gaseous and leads us to infer that it is only through prolonged integration and differentiation that the “elements” of the chemist have been produced.

Of the cosmical theories the nebular hypothesis of Kant and Laplace seems to be the one best suited to the present thought, in spite of the more recent theories that the heavenly bodies including our planet have been formed by the coming together of ice-cold meteors, or by gradual accretion through the continued accession of cold planetary matter in space.

According to the “ nebular hypothesis ” space is filled with matter in every conceivable state of integration and disintegration, its most primitive form being that of gaseous vapor in a state of incandescence. According to fixed laws, the forces of the universe act upon this gaseous vapor until it gradually collects more and more locally to form nebulous masses such as can be seen in various of the constellations. Through infinite time the nebulae become more and more condensed until, in obedience to the continually operating forces, they begin to rotate more and more uniformly, their vaporous particles to approximate more and more closely, and finally to coalesce to form fiery masses whose progressive integration passes from the gaseous to the fluid and finally to the solid state, and the formation of definite heavenly bodies.

When the forces acting upon the nebulous matter are uniform a single body may be produced, but when they are conflicting several may be formed, the smaller rotating about the larger in definite systems. The smaller bodies of the system are subject to the most rapid subsequent changes, so that in any planetary system bodies in all stages may be observed. This is, for example, supposed to be the state of our own solar system, in which the sun is still a gaseo-liquid incandescent body, some of the larger planets semi-solid, the

THE COSMICAL RELATIONS OF LIVING MATTER 19

earth solid and cool upon the surface, and its moon probably cold throughout. It is during the cooling and integration of such heavenly bodies that the differentiation of the component matter takes place. As this progresses, a multitude of combinations appear for a time, transform to new combinations, and so continue through an indefinite series of transformations, eventuating in things constituted as we now know them.

During these transformations certain substances appear whose stability constitutes the foundations of chemistry. Some of these occur in the elementary form, i.e., incapable of analysis into simpler forms, but more frequently they occur in combinations from which they can be liberated by artificial means and thus reduced to the elementary form. Some elementary forms combine with one another easily, others with difficulty. Some of the combinations are so unstable as to tend to break apart rather than to persist. Thus, among the chemical components of our planet we find a certain number, combined to form the rocks and soil, subject to little change, and to that only under peculiar circumstances, while upon the surface of the earth we find a small quantity of matter composed of elements entering into loose combinations and tending to perpetual change. The substances we call living, are included among these ever-changing combinations.

The most evanescent of these compounds comprise a group known as “ colloids,” many of which have a molecular composition, ascending in complexity until among the proteins we find “protoplasm” with a composition not yet definitely determined, but embracing O, H, C, N, S, and in some cases P.

This substance, protoplasm, constitutes the basis of living matter.

Chapter II. The Origin Of Life

The early philosophers of all nations referred human existence directly to our parents and indirectly to the gods, although it seemed to them a simple matter that the lower forms of life should come into being de novo. Belief in the spontaneous generation of the lower forms of life accentuated as philosophy slowly separated itself from religion. Greek philosophy is replete with expressions regarding the spontaneous generation of the lower forms of life, and the idea persisted through the middle ages to become a matter of paramount interest during the latter half of the nineteenth century.

The most superficial consideration of the subject is sufficient to show that among the ancients it was unfamiliarity with the lowly forms of life that led to such a notion, but more modern writers seem to have been led astray through the expansion of knowledge following the invention of the microscope which introduced them to a world of newer and simpler forms of life, and thus changed the problem. Thus, one possessed of the most elementary information upon natural history might scout the idea that such complexly organized beings as mice could be spontaneously generated, though the same difficulties might not at first stand in the way of conceiving that amoeba or bacteria might be.

As the conception of spontaneous generation has undergone modifications consistent with the evolution of knowledge in general, it is worth while to review the subject and see what it has meant, and what it now means to those who, is spite of all the evidence at hand, continue to adhere to it.

Among the ancient Greeks, Anaximander believed that animals arose through the stimulating action of moisture. Empedocles believed that all living things arose spontaneously. Aristotle, whose familiarity with natural history was much broader, does not subscribe to so general a view, but asserts that “sometimes animals are formed in putrefying soil, sometimes in plants, and sometimes in the fluids of other animals.”

Virgil in Book IV of the “ Georgies” describes the spontaneous generation of bees in the following language:

“First, a space of ground of small dimensions, and narrowed for this purpose is chosen; this they cover in with the tiling of a

narrow roof and with confining walls, and add four openings with a slanting light turned toward the four points of the compass.

Then a bullock, just arching his horns upon his forehead of two years old, is sought out; whilst he struggles fiercely, they close up both his nostrils and his mouth; and when they have beaten him to death, his battered carcass is macerated within the hide which remains unbroken. Then they leave him in the pent-up chamber, and lay under his sides fragments of boughs, thyme, and fresh casia. This is done when first the zephyrs stir the waves, before the meadows blush with new colors, before the twittering swallow suspends her nest upon the rafters. Meanwhile, the animal juices, warmed in the softened bones, ferment: and living things of wonderful aspect, first devoid of feet, and in a little while buzzing with wings, swarm together, and more and more take to the thin air, till they burst away like a shower poured down from summer clouds; or like an arrow from the impelling string, when the swift Parthians first begin to fight.”

Ovid, in his poetic account of the Pythagorean philosophy, commits its followers to belief in many forms of spontaneous generation:

“ By this sure experiment we know That living creatures from corruption grow:

Hide in a hollow pit a slaughtered steer,

Bees from his putrid bowels will appear,

Who like their parents, haunt the fields and

Bring their honey-harvest home, and hope another spring.

The warlike steed is multiplied we find,

To wasps and hornets of the warrior kind,

Cut from a crab his crooked claws and hide The rest in earth, a scorpion thence will glide,

And shoot his sting; his tail in circles toss’t Refers the limbs his backward father lost;

And worms that stretch on leaves their filmy loom Crawl from their bags and butterflies become.

Short of their feet at first, in little space

With arms and legs endued, long leaps they take,

Raised on their hinder parts and swim the lake,

And waves repel; for nature gives their kind,

To that intent, a length of legs behind.”

During the middle ages Cardan, in 1524, declared that water engendered fishes, and that many animals spring from fermentation. Van Helmont published special directions for the experimental generation of mice. Kircher describes and figures certain animals which he declares were formed, under his own eyes, through the transforming influence of water upon the stems of plants.

Children and ignorant persons still believe in the spontaneous generation of many living things and in the country districts many persons of otherwise good judgment believe that frogs and mosquitoes arise spontaneously in marshes, while the belief that a horse-hair placed in a water trough will be transformed to a threadlike worm, is widespread.

No one seems to have doubted that maggots were spontaneously developed in putrid meat until Redi became interested in the subject about 1680 and disproved it by a simple scientific demonstration:

“Watching meat in its passage from freshness to decay, prior to the appearance of maggots, he invariably observed flies buzzing around the meat and frequently alighting upon it. The maggots, he thought, might be the half-developed progeny of these flies. Placing fresh meat in a jar covered with paper, he found that although the meat putrefied in the ordinary way it never bred maggots, while meat in open jars soon swarmed with them. For the paper he substituted fine gauze through which the odor of the meat could rise. Over it the flies buzzed, and upon it they laid their eggs, but the meshes being too small to permit the eggs to fall through, no maggots generated in the meat, they were, on the contrary, hatched on the gauze. By such a series of experiments Redi destroyed the belief in the spontaneous generation of maggots in meat and with it many related beliefs.”

But in 1683 a new phase of the subject was opened by the discovery of bacteria and many other minute forms of life by Leeuwenhoek, and many scientific men to whom the spontaneous generation of fishes, frogs, or insects appeared to be an absurdity, were misled into believing that what was not possible for these highly organized animals might easily take place among such minute and lowly organized beings as those of the new world disclosed by the microscope. It seemed as if the threshold of life had been reached.

To the intelligent mind of the present day, disembarrassed of erroneous beliefs, it will at once appear that the size of the creatures has no influence upon the merits of the case, for there are minute organisms visible only to the microscope that are as complexly formed as others that may be inches or even feet in length. To the idea of simplicity of structure the mind may yield; it does at first seem more reasonable that an organism of extreme simplicity might arise spontaneously than that one of great complexity could do so.

So it seemed to these early scientists. The microscopic organisms were small, and in many cases of no visible complexity, and with few exceptions they seemed satisfied to believe that they arose de novo. So, in the nineteenth century we find the same convictions regarding the spontaneous generation of the slightly known forms of microscopic life that had been held hundreds of years before regarding the slightly familiar small but complex animals, and thousands of years before regarding all living beings.

But as time went on the world of microscopic life was scanned with improved instruments, and its population, when studied and classified, proved to be a miscellaneous one with varying structural complexity descending to a group so simple that correct classification seemed impossible. These ultimate beings appeared to be neither animals nor plants, and to have no definite place in the general scheme of living things. They were also innumerable, and their distribution apparently universal. Small wonder that it should have been thought a simple matter that what had so little structure, and was neither animal nor vegetable, could arise spontaneously under appropriate conditions. And, in passing, let it be noted that the appropriate conditions under which they appeared thus to arise were to be found in fermentation, putrefaction, and the discharges from morbid tissues — conditions that must recall once more the former beliefs about maggots, etc.

But there were some who conceived that the relationship between these minute entities and the conditions under which they were found were the reverse of those so generally accepted, and that instead of the minute organisms being generated through fermentative, putrefactive, and morbid conditions, the organisms initiated those conditions, increased in number as they progressed, and died out as they ceased.

Plenciz, a Viennese physician, greatly interested in the discoveries of Leeuwenhoek, was one of the first who assumed a causal relation between microorganisms and infectious diseases, and published this view as early as 1762. He also believed that decomposition only took place when the decomposable material became coated with a layer of organisms, and could only proceed as they increased and multiplied.

Needham, in 1749, firmly held to the belief that animalculae generated spontaneously as a result of vegetative changes in the substances in which they were found. He maintained that the bacteria that were seen to appear around a grain of barley kept in a carefully covered watch-glass, developed through changes incidental to its germination in the barley grain itself.

Spallanzani, some years later (1777), pointed out the slip-shod methods under which most of the so-called experiments had been performed, and supposed that he had proved spontaneous generation impossible by a new and improved technic. He filled flasks with various organic infusions, such as were supposed to be “ biogenic, ” subjected the contents to thorough boiling, hermetically sealed them, and then placed them under what were supposed to be conditions favorable to the development of life, but always with negative results. Instead of carrying conviction with them, these experiments of Spallanzani were severely criticized by Treviranus on the ground that the atmosphere so essential to life had been excluded from the fluids. To overcome this objection, Spallanzani gently tapped his flasks so as to produce minute cracks through which air might enter. When this was done, life invariably appeared and decomposition occurred.

The problem remained in about the same state until Schultze in 1836 improved the method by which air was admitted to the flasks. He filled them but half full of putrescible fluids, boiled them thoroughly to destroy such life as they might already contain, and then daily sucked into them a certain quantity of air that passed through a series of bulbs containing concentrated sulphuric acid or strong alkalies by which any germs of life that might be in the air should be destroyed. The culture flasks were kept from May to August, air being passed into them daily, yet without the appearance of life or putrefaction in the contained fluid.

Schwann in the following year (1837) performed a similar experiment with the same result, passing the air admitted to the flasks through highly heated tubes instead of through acids and alkalies.

Schroeder and van Dusch, in 1854, discovered that if the mouth of the flask containing a putrescible fluid was protected by a plug of cotton-wool through which an abundance of air could freely enter and exit, but by which it would be filtered, no life appeared in the contents.

The investigation was continued in 1861 by Pasteur, who showed that if the neck of a flask containing putrescible fluid was drawn out into a fine tube, bent down along the side of the flask, and then bent up again so as to form a V, it could be left open, after the contents of the flask had been thoroughly boiled, without danger of contamination from the outside air, which, entering through the

Fig. 1. — Flask used by Pasteur in his experiments upon the spontaneous generation of life. It was filled through the top which was then sealed. The contents, which consisted of putrescible fluid were then boiled, the side neck being open to permit the air to enter and exit. As the fluid cooled the side neck became closed by a few drops of water of condensation and prevented any germs of life from entering from without.

tubulature, would have any germs it might contain arrested by the drop of water of condensation that always collected in the angle of the tube.

Tyndall performed a most interesting series of experiments in which tubes were so placed as to project below the bottom of a closed chamber having a glass front and a glass window in each side. A rubber diaphragm was fixed in the roof through which a tube passed. Tyndall found that a ray of light passed through the side windows of the chamber was visible from the front because it was reflected from the dust particles suspended in the atmosphere of the box. After permitting the closed box to stand for a sufficient time, this dust was found to settle and the ray of light being passed through the side widow, finding nothing to reflect it, was no longer visible. When the contained atmosphere attained to this optical test of

Fig. 2. — Tyndall’s chamber for investigating the spontaneous generation of life. The front is of glass, as are the side windows, w. w. The optical test for the purity of the contained atmosphere is made by passing a powerful beam of light from the lamp, l, through the side windows. When the atmosphere contains no suspended particles, the tubes in the bottom are filled through the pipette, p.c. ( Tyndall .)

purity, the tubes fixed in the bottom were cautiously filled with putrescible fluids through the tube in the rubber diaphragm. When filled, these tubes, the bottoms of which it will be remembered projected below the bottom of the chamber, were heated by applying a pan filled with hot brine, and their contents boiled briskly for a time. When the chamber thus prepared was stood away, it was found that life rarely developed in the contents of the tubes and that no putrefaction took place. Thus Tyndall confirmed the work of Pasteur who in the meantime had been busily engaged in showing that there were “ organized corpuscles” in the atmosphere — the “floating matter” of Tyndall — which when admitted to the infusions caused them to putrefy.

Cohn had engaged in morphological studies of the bacteria and other low forms of life, and had discovered that many of them, under appropriate conditions, pass into a resting or spore stage. In many of the rod-shaped organisms a spot appeared in the rod, grew larger and larger, and became surrounded by a capsule. While this was perfecting its development, the rod in which it formed began to degenerate and eventually set it free. Thus there came into being a minute body — a spore. Further study of the spores showed that they abounded in the atmosphere and that many of them could endure temperatures higher than that of boiling water. It now seems clear that it was through the entrance of such spores into the infusions, their endurance of the temperatures to which the fluids were subjected during boiling, and their subsequent germination that the appearance of life in the fluids was to be referred.

Thus Harvey’s law omne vivum ex ovo which had long been accepted with reference to the higher beings became applicable to the lowest organisms in the modified form omne vivum ex vivo , and the doctrine of the spontaneous generation of life might be supposed to have received its death blow. The evidences thus collected were subsequently investigated by a great number of workers, by a great variety of methods, but with uniform results and at present almost every scientific mind is satisfied that life in the forms in which we now know it is never spontaneously evolved.

However, it remained to explain how, if all life descended from antecedent life, living things originally made their appearance upon the earth, and to those working under the influence of this necessity the new doctrine omne vivum ex vivo was not adequate.

The primordial appearance of life is too important a matter to be entirely neglected, so we are led to inquire whether the simplest forms of life known to us are in any sense primitive or whether they may not, in fact, be highly developed compared to the primordial forms from which they may have descended.

Here we are confronted by several difficulties, one of the chief of which is that our conception of “life” and of “living substance” is based upon those forms with which we are familiar, and whose manifestations we are accustomed to describe as vital. It does not by any means follow that only such are “ alive,” but it is only of such that we speak as alive, and only such that we can through the limitations of our conception of the term prove to be so.

It may not be unprofitable to speculate with Bastian and especially with Burke whether there may not be other, unrecognized forms of life, whose extreme simplicity of structure prevents us from recognizing them, eternally coming into and going out of being, leaving no descendants behind them, the power of reproduction which we customarily look upon as an essential characteristic of life being, in fact, only characteristic of such forms as shall have already evolved to a certain point.

It is also of some interest to inquire whether the phenomena of life are so different from other chemical and physical phenomena as to make us place the customary gulf between the living and not living, or whether they are not but a part of those universal phenomena by which we can in a certain sense attribute life to the world, to the solar system or to the universe itself!

It is almost certain that life is no longer being generated, and that its original appearance upon this planet took place under circumstances no longer existing.

biology: general ahd medical

Thus, conditions of temperature during past periods of the world’s evolution are believed by many to have been responsible for molecular combinations impossible at the present time. This is, however, conjectural, and not demonstrable. The chief argument in its favor is that all of our endeavors to see protoplasm come into being independently of antecedent life, have failed. We are thus obliged to conclude either that life never did arise spontaneously, or that it can no longer be generated spontaneously, or that we are at present unable to recognize the most primitive forms in which it occurs, being acquainted only with what are by comparison highly evolved forms.

References.

John Tyndall: “Floating Matter in the Air,” N. Y., 1882.

J. Butler Burke: “The Origin of Life,” N. Y., 1906.

H. Carlton Bastian: “The Modes of Origin of Lowest Organ-

isms, etc.,” Lond., 1871. “The Nature and Origin of Living Matter,” Lond., 1905.

Chapter III. The Criteria Of Life

Laying aside, for the present, all speculation as to the connecting links between the matter that we call living, and that which we declare to be not living, it becomes necessary to establish certain criteria by which the former be recognized. These distinctive properties have been formulated by Huxley as follows:

1. Its chemical composition.

The chemical composition of living substance is based upon a complex combination of O, H, N, and C known as protoplasm. It is a protein that is entirely unknown except as a product of living substance. Its exact composition is not determined because it is scarcely possible to study it apart from other elements by which and through which many of its functions are carried on. Chief among these are S and P.

2. Its universal disintegration and waste by oxidation; and its concomitant reintegration by the intussusception of new matter.

Life is accompanied by the manifestation of energy which implies combustion by oxidation, chemical disintegration of the complexly organized protoplasm, and its reduction into more highly oxidized but simple compounds, such as carbonic oxide and water. This would soon result in complete destruction of the protoplasm by analysis were it not within the power of the living substance to make good this loss as rapidly as it occurs.

When the living substance is young, the function of synthesis takes precedence over analysis and the organism is said to grow. This growth is, however, entirely dissimilar to that of the growth of crystals, for example, where it takes place by accretion, or the addition of new matter to the surface, for it pervades the entire molecular structure of the protoplasm by the actual interposition of the new molecules between those already existing. When the function of synthesis keeps pace with that of analysis, growth ceases, and when analysis is more rapid than synthesis, life soon becomes extinct and the protoplasm breaks up into simpler and simpler compounds.

3. Its tendency to undergo cyclical changes.

The cyclical changes are largely incidental to the phenomena of reintegration. Coming into being through the activity of antecedent living substance, the livingorganism proceeds to increase its own substance, to dispose of that which is formed in excess of its own needs by detaching it in the form of new individuals, and finally when no longer able to maintain the equilibrium of reintegration to disintegration, ceasing to live and undergoing dissolution by destructive analysis, but being survived by descendants behaving in the same manner.

The successful application of these criteria for the recognition of life presuppose some acquaintance with the supposed living substance. One cannot immediately employ them for the determination of the living or not living character of any particular object picked up haphazard during a ramble through the country, for, should the objects in question be inactive forms of life, such as the seeds of plants, not only would confusion arise from the evident dissimilarity of chemical composition occasioned by the presence of the starch, cellulose, and wooden materials forming the most conspicuous structures of the seed, but one would be at a total loss in an attempt to immediately accord to the seed any molecular activity or cyclical changes. A superficial acquaintance with seeds is, however, sufficient to enable the investigator to apply the second and third criteria