;:-.0 it is with Man. _V- regards his brain and hands he is the must -peel:Ili/v.1 44 mammals; but as. concerns his feet he is idalltigratle, show ing a tendency to loss of his little toe by atrophy, while already in the higher race he loses his wisdom teeth soon after they appear. Resides this be bears the vestige: of nearly seventy use less struetures, among them the vermiform ap pentlix, the most useless and positively dangerou pointing to his origin from some in4,re generalized mammal.
The ease is similar with the paddles of tin ichthyosaurus, the plesiosaurus, 'They are, at least in the last named. the result of moditicatiim by resulting in adaptation to the medium inhabited. And so it is with the process 111 evolution of the hull-. pterosaurs, and bats. and the mo4lilieations in the feet of the male, and in the burrowing insects. climbing lizards. mammals, particularly the lemurs. and the thumbless nunikeys.
There are four chief forms of degeneration: I Degeneration during the growth in dividual, and the phylogeny of the race or class: degeneration of the individual. more or less total; social and institutional degeneration, often affecting whole peoples, due to slavery. and to mental. moral, and pathological eau.(.; and (4) individual moral degeneration in the 1111 man races. resulting in the production of mental degenerates and crilninal•. It is worthy of ob servation that the 4,ceurrem.e of atrophy. of de generacy in man. is nearly everywhere foreshad owed in the rest of the organie world. where if is a normal proves:. and the nevessary complement of progressive evolution.
The death or elimination of the individual member whiell has become useless or out of harmony with its physical and social environ ment is also in the course of nature. \\lien once bipsed by atr441,11y. an organ or part of an organ eau never, as ? rule, be restored: there are a few exeeptions. e.g. that of the pigment of a blind Proteas subjected to light, and the organs of certain plants. The at an early stage be arrested. but after ;1 certain stage resumption of the original normal •l nurture becomes impossible. it not so, evolution would be vastly Irss progressive titan it has la en. and the world would be crowded More dl•tst ly than now ivith degenerates.
itnnIediate causes of degeneration are lack of nutrition, disuse, zia41 of habit and instincts, so that :in organ or set of organs are thrown out of use. .\trophy. ;11.0, as stated by l'ielimor, may arise Iron] lack Df space, as ....en in the reduction in the number of teeth in man compared with lemurs and platyrrhine monkeys. these having six grinding teeth. while loan has but live dim to a reduction in the size of the jaw.
Not only 11.) we observe sporadic cases of degell (ration, but ...peeks and genera, as well as families, are made up of forms in different stages of degeneration. All parasites, entire classes, as that of sponges, and two classes of worms, as the. Trematoda and Cestoida, the crustacean class Cirripedia or barnacles, and the parasitic fish-lice, as well as the parasitic isopods (Bopyrithe), and many insects owe their characteristics to degeneration, while the great order of Diptera arc all highly modified by the atrophy of certain parts, their most obvious features being the reduction of the second pair of wings so as to form the 'balancers.' (See
FLY.) The forerunners of the true vertebrates, the tunicates, afford a notable instance of the retrogressive development of an class.
Enough has been said to show how very gen eral throughout the animal kingdom is modifica tion by partial or total atrophy. The study of animals thus affected throws a flood of light on the factors and causes of progressive evolution.
In mankind, degeneration on a wholesale scale is observed in the effects of slavery and of the slave trade in Africa. where it has been carried on for centuries, and on the master races. The result is that the white race is in a degree pulled down, .or deteriorated. A parallel is observable in ant societies, where the service rendered by the enslaved tends to disuse and atrophy in the masters.
In the social evolution of man the joint work of Demoor. Massart. and Vanderville gives a multitude of fact: proving that, as among organ isms in general, so in human societies, evolution is at once progressive and retrogressive. Existing social forms have during the process of change and modification lost some parts of their struc ture, and this process of degeneration cannot be regarded as a return to the primitive condition of man. Thus. (1) an institution which has once disappeared in the course of human development never reappears; also. (2) an institution once re duced to the condition of a vestige cannot be reistablished and resume its former functions; (3) neither can it assume fresh functions, While in the organisms below man degenerative evolu tion is brought about by a limitation of nutri ment, in sociology the cause is a limitation in capital or labor. An institution which has ceased to be functional or useful may survive. These survivals exist here and there. and. as llonzeau has said. "it is to he expected that liv ing and superior civilizations drag behind them a trail of &Ink from dead civilizations." All t'.is has the most significant hearing on human degeneracy and the study of criminology. espe cially as to the existence of those pathological, mental. and moral degenerates that appear to live only to afflict struggling humanity.
There are degenerate races, as the Australians, a probable branch of the Dravidian stock of India; the Gypsies, a broken-down low-caste Indian people; the Fuegian:, a tribe segregated from the American Indian race. There are also through the most highly developed civilizations physical. mental, and moral degen erates, of which families like that of the ,lames brothers of Missouri. the Juke of flit- State of New York. or assassins like Booth. Cuitea n. and certain Nihilists are examples.