Degeneration (biology)

“ Thus, to the other causes of degeneration in animal life and structure, we may append that which takes origin from the extreme or excessive development of one function over another. Physiological development in one direction, overstepping the natural and ordinary limits, runs concurrently with destruction of life's equilibrium, and naturally tends to produce degeneration and simplification of other organs and other duties of life. ”

“ The category of life's extension includes, in fact, many possibilities which at first sight might appear of most unlikely kind; and, among these possibilities, that of extreme degeneration is by no means the least notable as an element in inducing the material variety of life we behold in the animal and plant worlds of to-day. The list of causes which lead to the degeneration of living beings includes, however, other fashions of producing retrogression than by fixation and parasitic habits, and operates in different ways upon organisms of varied structure and social or biological rank. ”

“ When under any kind of noxious influences an organism becomes debilitated, its successors will not resemble the healthy, normal type of the species, with capacities for development, but will form a new sub-species, which, like all others, possesses the capacity of transmitting to its offspring, in a continuously increasing degree, its peculiarities, these being morbid deviations from the normal form—gaps in development, malformations and infirmities. ”

“ It was the ultimate product of mammalian degeneration; the frightful outcome of isolated spawning, multiplication, and cannibal nutrition above and below the ground; the embodiment of all the snarling chaos and grinning fear that lurk behind life. ”

“ We have seen that degeneration, or the simplification of the general structure of an animal, may be due to the ancestors of that animal having taken to one of two new habits of life, either the parasitic or the immobile. Other new habits of life appear also to be such as to lead to degeneration. Let us suppose a race of animals fitted and accustomed to catch their food, and having a variety of organs to help them in this chase—suppose such animals suddenly to acquire the power of feeding on the carbonic acid dissolved in the water around them just as green plants do. ”

“ All are agreed that the important point is degeneration beyond the point reached by panmixia, the establishment of the degenerating process, whatever it may be, in the germ, or, in other words, the breaking of the power of heredity. ”

“ Tissues and organs degenerate in individual animals, as animal frames retrogress in their entirety. Cells retrograde and fibers degenerate in our bodies, just as the sea-squirt's frame exhibits, as a whole a universal, physiological backsliding. Nor may many of our diseases alone be esteemed mere examples of degeneration affecting our tissues. The termination and decline of life itself and the age that really "melts in unperceived decay" are, in reality, examples of natural degeneration also. The decline of existence is largely a retrogression of structure. ”

“ As the brain is the last acquirement in vertebrates, considered from the standpoint of necessity, while the face (also a late acquirement) is much less complex, the last, obviously, will present the derangements from degeneration in shape, while the former will show these in shape and function. Furthermore, during the embryonic period the development of the brain will, of necessity, be more immediately affected by degeneracy than the face, which will gain in evolution at its expense. ”

“ A differentiation of parts, which286 leads to a partial degeneration, and finally even to the loss of individual organs, is, when looked at by itself, a degeneration, but yet may be advantageous to the organism in the struggle for life. ”

“ One word on an important side-issue—the problem of evil in man, of stagnancy and degeneration in organic evolution. Degeneration often does occur—a reversal, in other words, of the main tendency. But the positive fact remains that the maximum level is progressively raised, and that we find that stagnation of development and even sometimes degeneration have been factors indirectly helping on the main direction. ”

“ We may now examine a few examples of undeniably degenerate animals, and first, I may call to mind the very remarkable series of lizard-like animals which exist in the south of Europe and in other countries, which exhibit in closely related genera a gradual loss of the limbs—a local or limited Degeneration. ”

“ It consists in the study of the laws of physical degeneration,—the stages and manifestations of the process by which Nature dismantles the complete and typical human organism, until it becomes too bad for her own sufferance, and she kills it off before the advent of the reproductive period, that it may not permanently depress her average of vital force by taking part in the life of the race. ”

“ By degeneration should be understood the loss of the hereditary qualities that have determined and fixed the characteristics of the race. The characteristic of what is called in human races morbid heredity, which is simply a degeneration, is an abnormal tendency to variation in the posterity, which becomes, in consequence of physical, mental, and moral faults, progressively capable of adapting itself. In the artificial races of domestic animals the result of degeneration is often reversion to a primitive type of the species with capacity to recover the old adaptations. ”

“ The factors underlying the stable state force the animal to remain as it is; those underlying the progressive tendency make it more elaborate, while the factors of degeneration, on the other hand, tend to simplify its structure. It requires no special thought to perceive that progress is a great fact of nature. The development of every animal and plant shows the possibilities of nature in this direction. ”

“ Notice how by specific instances the following selection illustrates the truth of the generalization set forth in the second sentence and restated in the last sentence.
DEGENERATION THROUGH QUIESCENCE While parasitism is the principal cause of degeneration among animals, yet it is not the sole cause. It is evident that if for any other reason animals should become fixed, and live inactive lives, they would degenerate. There are not a few instances of degeneration due simply to a quiescent life, unaccompanied by parasitism. ”

“ As the biologists tell us, the atrophy of an organ, which we call degeneration, is itself a step in the progressive adaptation of the organisation to new conditions of life, and, as the moralists remind us, in the ethical sphere a “fall” is, in its way, an upward step. ”

“ If this notion be accepted, then is the idea of degeneration as a normal phase of life rendered still more feasible and plain. Reaching to the individual and to the species as well; extending and including in its scope the lowly organized as well as the higher being; affecting one group or class lightly, and influencing another wellnigh to the complete exclusion of progress, we find degeneration and retrogression to be numbered among the stern realities of existence. ”

“ Considering the matter more closely, we find that the vices in the conformation of degeneration, which we call the stigmata of degeneration, are teratological deformities. If the degenerate fails to give origin to beings that resemble him, it is not because he has acquired the special faculty of transmitting characteristics that do not belong to him, but because degeneration is the dissolution of heredity. ”

“ It is quite possible that animals with considerable complexity of structure, at least as complex as the Ascidians, may have been produced by degeneration from still more highly-organized ancestors. Any group of animals to which we can turn may possibly be the result of degeneration, and yet offer no evidence of that degeneration in its growth from the egg. ”

“ In other fields, wherever in fact the great principle of evolution has been recognised, degeneration plays an important part. In tracing the development of languages, philologists have long made use of the hypothesis of degeneration. ”

“ The healthy, functionally valuable tissue passes at last into the condition of degenerate, comparatively useless tissue. The force of heredity will long lead to the production in the embryo of the structure which, in the ancestral days of healthy exercise, was to be of service to the organism. At this stage of life the conditions have not changed. The degeneration sets in at that period when the ancestral use is persistently denied. There is no reason why "disuse" should in all cases remove all remnants of a structure ”

“ Any new set of conditions occurring to an animal which render its food and safety very easily attained, seem to lead as a rule to Degeneration; just as an active healthy man sometimes degenerates when he becomes suddenly possessed of a fortune; or as Rome degenerated when possessed of the riches of the ancient world. The habit of parasitism clearly acts upon animal organisation in this way. Let the parasitic life once be secured, and away go legs, jaws, eyes, and ears ”

“ Nay, stranger still is it to discern that the full flush of life's vigor is accompanied by degenerative changes as typical as those which mark life's decline. For every tissue wastes as it works; and cells degenerate, die, and are cast off from every surface and tissue of our frames as the natural result of living and being. "Generally speaking," says a writer, in discussing the degeneration of human tissues, "those parts which live most slowly are those of which the duration is the greatest, and in which there is consequently the least frequent change. ”

“ Degeneration is a necessary part of the process of organic evolution. All progress, whether anatomical, intellectual, or social, takes place through selection, and selection means the pining and ultimate passing away of that which is left. In individual evolution it is organs, ideas, and traits of character that are eliminated, and in social evolution it is customs and institutions. ”

“ Many of the directly inherited impulses, again, appear both in man and other animals at a certain point in the growth of the individual, and then, if they are checked, die away, or, if they are unchecked, form habits; and impulses, which were originally strong and useful, may no longer help in preserving life, and may, like the whale's legs or our teeth and hair, be weakened by biological degeneration. ”

“ Powers of nutrition, division, and conjugation with unrelated forms comes to a standstill. This senile degeneration is very interesting. The first symptom is decrease in size, which may go on till the individuals may not measure over a quarter of their normal proportions. Various internal structures then degenerate until at last we see formless abortions incapable of living and reproducing themselves."—Thompson, Elements of Zoology. ”

“ Such animals, which hitherto had possessed a well-developed nervous system and quick organs of sense, as well as the power of moving freely, lose these when they accustom themselves to a parasitical mode of life; they consequently retrograde more or less. There the differentiation viewed by itself is a degeneration, although it is advantageous to the parasitical organism. ”

“ Nevertheless, it cannot reasonably be doubted that all the bodily signs or ‘stigmata’ of degeneration, all the arrests and inequalities of development that have been observed, have their origin in a bio-chemical and bio-mechanical derangement of the nerve-cell, or, perhaps, of the cell in general.
In the mental life of the degenerate the anomaly of his nervous system has, as a consequence, the incapacity of attaining to the highest degree of development of the individual, namely, the freely coming out from the factitious limits of individuality, i.e., altruism. ”

“ It is seen, then, that a state may be at the same time diseased and yet the mere return to what was primitively a perfectly healthy state of things; and it was with culpable frivolity that Lombroso was reproached with contradiction because he saw in criminal instincts at once degeneracy and atavism. The disease of degeneracy consists precisely in the fact that the degenerate organism has not the power to mount to the height of evolution already attained by the species, but stops on the way at an earlier or later point. The relapse of the degenerate may reach to the most stupendous depth. ”

“ The statement that the hypothesis of Degeneration has not been recognised by naturalists generally as an explanation of animal forms, requires to be corrected by the exception of certain kinds of animals, namely, those that are parasitic or quasi-parasitic. With regard to parasites, naturalists have long recognized what is called retrogressive metamorphosis; and parasitic animals are as a rule admitted to be instances of Degeneration. ”

“ The knowledge acquired by the individual becomes hereditary, transforms itself into an organized faculty of the species, and the organism feels subjectively, as a discomfort which may amount to pain, the warning that a pernicious influence is acting upon it, and that it has to avoid it. To escape from pain becomes one principal function of the organism, which it cannot insufficiently provide against or neglect without expiating that negligence by its ruin. ”

“ The stigmata of degeneracy, therefore, most likely to attract attention are in the order given, those of the face, jaws, and teeth; ear, eye, cranium; body, bodily functions; brain and spinal cord. Under these last are to be included their mental and nervous functions.
The following table summarizes in practical form these stigmata [65] :—
The factors producing degeneration act by causing nervous exhaustion in the first generation. ”

“ Degeneration may be defined as a gradual change of the structure in which the organism becomes adapted to less varied and less complex conditions of life; whilst Elaboration is a gradual change of structure in which the organism becomes adapted to more and more varied and complex conditions of existence. In Elaboration there is a new expression of form, corresponding to new perfection of work in the animal machine. In Degeneration there is suppression of form, corresponding to the cessation of work. ”