Popular Science Monthly/Volume 46/November 1894/Some Analogies and Homologies
| SOME ANALOGIES AND HOMOLOGIES. |
By W. T. FREEMAN, F. R. C. S.
READERS nowadays like to have things made easy for them. The student has worked for year after year at one new subject after the other; it has been hard work for him, he has painfully struggled to master the new facts, the new ideas, and the time comes when he has reached the acme of his work; he thinks more for himself, reads magazines more than books, and prefers to digest the articles in his armchair, and they must be put for him in an appetizing form, must reach him in fact as the old ideas amplified and reclothed. Very pleasant reading the old lore brought home again, very refreshing to regain what is nearly lost by the help of a few chatty words in every-day tones; nice to dream, even among the words of the scientist, and to drift into illusive paths of speculation which are pointing dimly through and away beyond the veil of thought. May this little paper then be simply a series of dips here and there into the teachings of the unity of type and ideas, leaving the workings of the deeper mines for those who are fit for the labor.
Analogues and homologues are words with a practical ring about them, but they can not always be dealt with in a practical manner. The analogies of the creation teach us that everything is spun of the same stuff and upon one plan. Let a powerful example of this fact be taken in hand at once, and some portion of the animal creation be utilized. Now, we have all of us necks, some of us graceful necks, some of us apoplectic necks, and some of us no necks at all to speak of; again, the giraffe has a very long neck, the elephant a very short one, and the porpoise apparently stops short of one altogether, but in each and every case we find seven cervical vertebræ—and seven only. Again, they, and human beings also, all have the same number and variety of muscles and ligaments. Some of them certainly are simply mere representatives; for instance, the powerful ligamentum nuchæ of the horse is but very feebly represented in man. "Padding" accounts for all the rest—a little more or less of fat and cellular tissue.
"Every face however full,
Padded round with flesh and fat,
Is but modeled on a skull,"
and it tells the same tale of the rest of the figure. It seems an odd statement at first sight, but there are many millions of beings who have an outside instead of an inside skeleton. What a miserable existence these poor creatures must have if they have a good figure, for it can not be exhibited! The lobster is of the 40-exoskeleton type.
I have dealt with necks, now for the other extreme. It might be argued that one great difference between ourselves and the rest of the vertebrates is marked by the fact of our having no tail. We all have tails. 'Tis true they are wretched specimens, but they exist universally. We do not wag our tails, but only the other day I spoke with a gentleman who had a dog whose caudal vertebræ were anchylosed together. A little careful selection with this dog, and it is probable that a race of dogs might be developed with an os coccygis like ourselves. Disuse invariably leads to abortion. The little mass of anchylosed vertebræ that we call the OS coccyx is our best apology for a tail, but this region of the spinal column becomes wonderfully modified and developed if we compare it with its homologue in other members of the creation. It may act as a hand, may be the exclusive locomotive organ, it may contain the only free vertebræ in the body. In the spider monkey it is prehensile and is often used as a hand. In some sharks the number of the vertebræ amounts to two hundred and seventy. In tortoises the coccygeal vertebræ are the only free vertebræ. In the sole the neural spines and the hypophyses are remarkably developed. Finally, the bone may be even more rudimentary than in man. In the bat there are but two coccygeal vertebræ.
Quite a developed tail has, says Marshall, been discovered in the human race in certain rare and anomalous cases.
In the embryonic stage of the vertebrates the spinal column is represented by the so-called notochord, and this notochord is temporarily represented in the Ascidians, a class of animals bearing not the remotest resemblance to the Vertebrates. This is a highly interesting fact in connection with the interrelation of species.
One other most interesting fact: At an early period of our development—that is to say, at an early part of our embryo existence—the os coccyx is free and projects beyond the lower extremities.
One other less interesting fact: What tail we have is always carried between our legs—no doubt, in the majority of instances, there is good reason for it! Our limbs form beautiful subjects for comparison. Throughout the vertebrates they never exceed four in number. They are all modifications of one type, whether we take the fins of fish, the wings and legs of birds, fore and hind legs of quadrupeds, or arms and legs of man. Comparing the leg of a bird with the leg of a man, we see that the complete leg of a bird shows first the thigh bone, then the tibia or lower leg bone, and then in the place of the tarsus and metatarsus a single bone, with, at its lower extremity, a small bone supporting the four toes. Primarily the analogy between the last five bones of the bird and the so-called tarsus, metatarsus, and toes of man does not seem very complete, but if the chick in the egg, be examined, its leg will be found to consist of the thigh bone, of the tibia, of two tarsal and three or four metatarsal bones, and the toes or phalanges. The upper tarsal bone subsequently becomes anchylosed with the tibia and the lower one with the consolidated metatarsus. Now the analogy becomes much more complete.
The horse has but a single metatarsal bone (the third), with rudiments of the second and fourth. These rudimentary metatarsal bones of the horse are very interesting. By means of them it is comparatively easy to trace out his descent. I may be pardoned for mentioning such well-known facts and analogies as the following, among the vertebrata—that the whale possesses the rudiments of hind legs, that the boa constrictor possesses also the rudiments of a leg and a pelvis, and that the rudiments of the wings are discoverable in the apteryx.
A few other animal analogies: The third eyelid of the bird exists also in some amphibians and reptiles and in sharks; also in man as a rudimentary structure.
The manner in which cows, deer, and sheep tear up the grass when they are feeding, plucking away at the tufts, is familiar to any observant man. The incisors of the upper teeth are wanting. The interesting analogy is the fact that the teeth are really there, but they are uncut—that is to say, they have never pierced the gum.
The skin with its appendages forms a beautiful story of analogy. Our own microscopical epidermic scales are. strictly comparable with the cells that make up the scales of fish and of reptiles; their further development into hairs and, nails again compares with the feathers of birds and the hooves and horns of animals.
We call ourselves a hairless race; but everywhere on our bodies are the small lanugo hairs. Stimulation will readily cause these hairs to grow to any extent The surgeon has frequent opportunities of witnessing this retrograde progression toward a lower type.
Molting has its analogy throughout the animal kingdom. We indeed molt invisibly, are continuously shedding our scales, but there are some animals that get through this process even more quickly than do birds, as, for instance, the shedding of the skin as a whole by the newt, eft, and snake.
Sir James Paget has noted that some people have a few extra long hairs growing out from the general mass of the eyebrows. These few long hairs are representatives of a permanent condition in the chimpanzee and some baboons. they grow out separately from the general hairy mass over the superciliary ridges.
Darwin notes as a significant fact that the palms of the hands and the soles of the feet of man are quite naked of hairs, like the inferior surfaces of all four extremities in most of the lower animals.
Something about the ear. The lobule of the ear is peculiar to man: there is, however, a rudiment of it in the gorilla. Happy gorilla—and man!
About the brain of man and apes. The whole comparison is one of degree, and in the case of the Bushman's brain with that of a well-developed ape, the comparison becomes nearly equal. Richard Owen once claimed that the hippocampus minor, a trifling portion of the interior of the brain, was the only exclusively characteristic human part, but it has since been demonstrated in the orang and chimpanzee. In truth there are no specific distinctions between the brain of the ape and that of man! I possess in pickle the brain of a monkey; I am sure that my own brain is of much greater proportional weight and complexity. It is a pleasing reflection!
To turn to a totally different class of analogies, picking them out and noting them from the thousands of examples in the world of manners, thoughts, and ideas. The effects of civilization and town life upon man and some of the lower creation is very well exemplified by the town sparrow being seldom caught by a cat or slain by a missile, while the bumpkin bird is easily overtaken by the one or the other. Experientia docet—at one time the gulls of the Serpentine used to slay the sparrows; they knew not their enemy, but with each new generation of their victims the gulls had fewer meal. Instinct has been described as the accumulated experience of the race. We have had a good example of it here; that it is common enough among the different races of mankind and the various animals of the creation goes without saying, and Dr. Taylor nearly, proves that it exists among plants.
Parents watching the characters of their children observe that at one time the traits of the mother are to the fore, and that at another period of the child's existence he or she shows the chips of the old block by exhibiting some mannerism or peculiarity of the father. Apparently the male points are as easily inherited as the female points, and most certainly when the male tendencies are most evident, then the female tendencies are more or less in abeyance, and vice versa, and these variabilities may of course occur at any period of the being's existence, often, alas! when least desired. It has been disputed whether the female points of a plant are not more readily inherited than the male. A few years ago it was stated that the chances were as much as three to one in favor of the female side. Messrs. Sutton's foreman has experimented on these lines, particularly with wild potatoes and a cross with gloxinias. He seems convinced that the hereditary traits of the male are shown as often and as decisively as those of the female. But he is also convinced that, while the staminal tendencies are to the fore, the pistillate tendencies are more or less in abeyance. For a considerable period of the plant's growth he has noted nothing but the male tendencies; suddenly the whole bearings of the plant have changed, the staminal tendencies have absolutely died off, and a plant with all the traits of its mother rapidly shows up in its place.
The reasons why a plant should always be called a plant, and an animal an animal, are not always very apparent. An animal is a conscious being. I mean that it knows how to discriminate between this and that, reasons about what is good for it, rejects what experience has informed it is not good for it, and has special sences. It is a conscious being—indeed reasons, discriminates. Here is a great gulf between the animal and the plant! Most of us are ready to acknowledge such simple truths, and we are all wrong, for the differences when sifted are only those of a greater and lesser degree. Some plants like shade, some like light. Why? Well, why do we under some circumstances prefer dark, and under others light? When we are healthy we can digest meat, and reject, with good reason, a meal of sticks and stones. A carnivorous plant receives and digests a proportionate meat meal, but feed it with pebbles and bits of stick, and it refuses to receive such dainties. We bend beneath a blow, we protect ourselves from further injuries that we judge may follow—so do the sensitive plants. With the aid of a specialist in this class of work I am trying to demonstrate the presence of nervous tissue in plants. So far, we have not been successful, but the circumstantial evidence is so strong that we may feel quite certain that better methods of demonstration will give ocular evidence of what we seek. The proofs of the struggle for existence in both animal and plant life have been prettily told by Taylor.
The part that color and get-up plays in the propagation of species is precisely analogous, alike in the doings of man, the lower animals, and plants. This I have more thoroughly touched upon in a previous paper.[1]
The perfumes attached to plants and the animate creation are in both instances used for like purposes, generally to attract, sometimes to repel.
The feasting and temporary entrapping of the flies within the spathe of the arum until the pollen has been dusted upon their backs for distribution, have been compared to the feasting of the old-day voters at the candidate's expense.
The intermarriage of near relatives, or the interbreeding among home flocks, is most disastrous in its effect upon the offspring. Plant life appears to be aware of all this, and adopts the most startling devices for its confutation. Some of these devices are worth tabulating:
I. Staminate flowers, pistillate flowers—these may be monœcious or diœcious.
II. Pistils elevated above the stamens.
III. Pistils arranged at different heights, as in the pin-eyed and rose-eyed roses.
IV. Different sizes and lengths of both stamens and pistils, as in the purple loosestrife.
V. Their own pollen acts injuriously to the pistils of some flowers, as in the primroses.
VI. Most startling observation of all—the pistil is cleft and the two stigmatic portions are maintained closed until the pollen of the flower is removed—as in the salvias.
VII. The catkins of the oak are beautiful devices for the winds of spring to scatter the pollen.
VIII. The facts collected by Darwin in the natural history of orchids.
IX. The milkweeds are said to be able to discriminate between those insects that will be able to cross them and those that will not. Their vengeance upon the useless intruder is indeed vindictive—they seize upon and hold him till he dies.
X. The stamens and pistils do not always ripen at the same time.
XI. In order to save their own increase and insure crossing, some flowers denote to insects an absence of honey by a change in the color of their petals.
Ah observant gardener informs me that races of plants improve and improve by proper cultivation and care until they reach their zenith. The zenith being reached, the greatest care is necessary, lest the decline should begin; but, with the necessary amount of care, the height of their prosperity may be prolonged indefinitely, but once the decline begins, the fall to probable extinction has inevitably commenced. How well may this be likened to the career of nations! Internal dissensions and the agitator's wile may ruin the backbone and trade of a country, and hasten on its fall. The noble and broad-minded statesman is the conscientious and hard-working gardener striving to outwit the enemies and parasites of his time, saving and enwreathing his cares in the glory of the achievements of the past.
The animal moves—most gifted and superior animal that possesses a power which the plant does not! Is this a truism? Among many kinds of fungi, water-weeds, sea-weeds, mosses, and even ferns, the spores and male organs actually possess locomotive power, and by means of cilia and flagella are able to move from the parent plant, and distribute themselves to some distance.
The suicidal mania is apparently appreciated by not man only. In Africa, ants have been seen marching by thousands for days together into a stream, and being swallowed by crowds of fish as fast as they could get into the water. Butterflies have been known to migrate in numbers to the sea. Similar tales have been told of rats.
We say that the existence and possession of a soul, the something that dogmatic theology asserts can exist after the death of the brain, after the death of the individual, is the attribute of man alone, and marks him as the head of the creation. Every thought that passes through our mind, every effort that guides our pen, is brought about by the molecular energy of the brain and of the muscle cells; this power is dependent upon the proper nutrition of these cells and of the body as a whole. Starve the tissues of the brain and muscle—thought no longer flows, the pen is no longer guided. The lower animals think, move, have instinct; they are conscious of ill or wrong, of joy and remorse, and herein lie the totalities of the soul. Soul is only the name for a mystery that we can not explain, and this mysterious combination which leads us to dwell upon a life devoid of mechanism, a life freed from the trammels of matter, with its repellent forces and energies, surely belongs to us only in degree. What rights have we, what proofs have we, to help us to assume to ourselves a one exclusive evolving soul, fitting itself for a newer and purer existence, and yet to deny all that we base our hopes upon to the whole of the rest of the creation? Surely the lower animals have their degree of soul, and a chance of a lesser heaven as well as our important selves. Our thoughts and actions are bestial, only too often to a loathsome degree; and on the other hand not only the ape world, but also still lower creatures, point us daily many a useful moral or loving lesson. Does the existence of the soul mark the gulf that separates man from all other living beings? Does the lowest Bushman of to-day possess a soul denied to the highest anthropoid ape, and if he does not, who shall draw the line where the animal is separated from beatified man? not man, at all events.
In the frightful and only too common form of insanity, "the general paralysis of the insane," at different periods the actions and behavior of the unfortunate patient become horribly monkey-like. The continuous chattering, the restless clawing movements, and the stage at which the food is seized and crammed into the mouth, and, too, the half-childish, half-monkey-like gibes and smiles which wreath the poor wretch's features as he pours his grandiose ideas into the listeners' ears, create a sickening impression for the observer to think upon.
A little more old lore concerning apes and man, including a little recapitulation.
Man compares with the anthropomorphous apes in that the relative weight of a Bushman's brain compared with that, say, of an ordinary gorilla is only as three to two. The furrows and convolutions are really the same in both, and the ape does possess a hippocampus minor. The anthropomorphous apes possess, as do men, five molars; this of course includes the bicuspids with the molars. Even a prehensile toe is not unknown as a human attribute—i. e., the tendency to oppose the big toe to the others. In the gorilla especially the contrast between hand and foot is nearly as distinct as in man. Then again there is the discoidal placenta with, as in the chimpanzee, its two umbilical arteries and one umbilical vein. It is to be noted that the anthropomorphous apes differ far more from the lower apes than do they from man. Lucia and others have said much regarding the fact that the ape as he grows becomes more bestial, and man more human.
Man's descent from the ape is not direct; apart from this, the laws of heredity forbid the retrogression of the one species to any great extent, or the exaltment of the other. Man's kinship, however, is not upset by the bestial strength of the teeth of the ape, or by the enormous protuberances on the skulls of this animal. The embryonic and youthful skull of the ape exhibits a plastic and well-formed cranium. Later, in form and character, it strikes out into a divergent and disastrous path.
Two of the supposed great distinctive marks of division between plants and animals are now disproved. Cellulose was believed to be found alone in vegetable tissue, but now starch, chlorophyll, and cellulose are known to occur in the lower types of the animal kingdom. Animals were supposed to subsist only upon ready-made organic material, while plants were known to be able to convert inorganic into organic material. This partition wall has also been overthrown.
Stinging and prickly plants may be fairly said to possess and use weapons of defense. The sensitive plant, too, in a timid manner resists to the last the attacks of its attackers, and I am convinced that it appreciates the current from an electric machine. I have tried to reason with myself that my observations have been fanciful, and have been forced to the conclusion that these plants possess not only nervous ganglionic centers in their leaves, but cords of communication running even to the stem, where possibly there may be the rudiments of a spinal cord communicating, may be, with other ganglia in the roots, the totality of which would represent a brain. Nuclei and tracts of special sensations (unless they be special plant sensations), apparently, they do not possess—I mean such sensations as sight and hearing. They are, to some extent, sensitive to a breath of wind when no actual contact takes place.
Men are wise in their generation—the wisdon of man is indeed a remarkable trait of the creature—but the weather wisdom and the immigration wisdom of birds are traits equally remarkable. If the bird lore is due to the accumulated experience of the race, just so much can be said also about the wisdom of man.
Man loves alcohol; man includes the teetotaler who loves alcohol also, but who most wisely refrains, as he doubts his own powers of resistance to excess. Here, possibly, there is a gulf between man and the lower animals. The lower creatures, as far as I know, never refrain from alcohol in excess, if they can get it. Many tales have been told of alcoholism in the lower animals, none of moderate drinking, if the alcohol were available; therefore, perhaps, the only great difference between man and the lower animals is that man may be a moderate alcoholist. Monkeys are peculiarly fond of arrack and such stuff. Possibly, therefore, our own love of spirits is simply an unfortunate hereditary ancestral trait.
Comparisons are at the best odious; however, the most tender of us can always console himself by remembering that the comparison between man and animals and plants is only reasonable when we descend, as far as man is concerned, to the very lowest species of humanity, and even then he has to be compared with the highest type of the creatures below him. Therefore, indeed, what magnificent creatures we are—or, anyhow, might be!
I have seen dogs and, I think, other animals gazing abstractedly at and evidently following something. They were troubled, sometimes whining, or positively crouching in awe or dread. Such behavior in a dog during the course of a long life is not uncommon, and it would be ridiculous to declare all such dogs to be rabeitic. I believe other animals suffer from illusions. I know two men with whom I have spoken, and who are reasoning, rational beings, and otherwise very practical, who are able to make a chair waltz round the room or go up-stairs without in any way, directly or indirectly, having contact with it. Having started the chair on its career, it is kept going by mere suggestion. I question and cross-question these gentlemen, and before witnesses, and they maintain their assertion stolidly; and I believe that they do see in their own mind the chairs doing all they say; but what this peculiar condition of mind implies I know not. To the majority of readers such tales appear mere vaporing. I can offer no explanation, except that these visions are not delusions, for the perpetrators are reasoning beings and sane; they are not illusions, for such gentlemen (and ladies, too, I believe, but I have not met them) believe that they are actually moving solid furniture merely by the force of their own suggestion. Such acts, so interpreted, appear to me to be only able to be likened to those of a deity—and a deity is beyond our comprehension. They are not due to animal magnetism. They are not dreams. The effect of suggestion by means of "hypnotism," with its startling results, has been witnessed by thousands, but any similar explanation breaks down here. If these things be true, then the connection between the animate and inanimate creation is complete. For obvious reasons, names can not be introduced into such a paper as this; but I believe that I could gain an introduction to one or both of these gentlemen for any person, sufficiently well known, and desirous of investigating such material.
The lower animals, then, in a degree, do almost all that we can do. Plants do many things that were once considered to be solely the doings of the animal creation. The ultimate sitructural elements of either will some day assist in the formation of mountains and seas. Therefore, indeed, we are all one—animal, plant, mountain, sea. The component elements and molecules of the animal and plant creation have simply become highly idealized and specialized. The marked difference between man and a mountain lies in the constant dissipation of energy by man and its passive retention by the mountain. The mountain is a mere reservoir of energy; man one of the compounds of elements used for the dissipation of energy.—Gentleman's Magazine.
- ↑ See Something about Natural Selection, Gentleman's Magazine, August, 1892.