43 6 THE POPULAR SCIENCE MONTHLY. 



Optimists assure us that even if insanity, idiocy, deaf-mutism, blind- 

 ness, and intractable disease and deformity be upon the increase, the 

 evil is not unmingled with good, as it at once serves the twofold pur- 

 pose of illustrating and exercising the benevolence of the age. 



The only rational interpretation that can be put upon the manifes- 

 tations of defective blood is, that they are the prodroma of its extinc- 

 tion. If the genetic conditions are continuously applied, such will be, 

 as familiar experience often illustrates, the ultimate result ; the salient 

 points of the process being, a large infant mortality, death before re- 

 production, and infertility. On the theory of Dr. N. Allen, that in- 

 crease of pojmlation is mainly governed by the law of approximation 

 to perfection in bodily structure and harmony of function, the postu- 

 late can be easily proved that, as a people, we are gradually but surely 

 degenerating. Dr. Toner, the compiler of vital statistics at the na- 

 tional capital, has found that "there is undoubted evidence of a grad- 

 ual decline in the proportion of children under fifteen to the number of 

 women between fifteen and fifty years of age throughout our country." 



The vital statistics of Rhode Island have been carefully and intel- 

 ligently collected for many years by Dr. Snow, who states that there 

 has been a gradual decline in the birth-rate among those of American 

 parentage for the last twenty years. The same is true of Massachu- 

 setts, and, in fact, of New England ; the birth-rate being actually 

 lower than in any country of Europe, France alone excepted. 



The causes of race degeneration are usually very complex ; some 

 pertaining to environment, others to a faulty personal hygiene. 

 Through heredity all the evil effects are accumulated and perpetu- 

 ated. But fortunately there is a principle in life which tends to an- 

 tagonize and obliterate the destructive tendency of these innate de- 

 fects upon life. If nothing of the kind existed if there were no 

 opposing force the failure of physiological action would be rapid, 

 uniform, and progressive, until morbid energy gained its fatal mastery 

 over that which tends to hold organic structure in a cycle of harmoni- 

 ous changes. 



What is known as reversion, and termed by Darwin " the great 

 principle of inheritance," furnishes the clearest conception of this op- 

 posing energy. Of its essential cause nothing is known, but as to its 

 steady operation there is indubitable evidence. In two well-defined 

 conditions of organic life, its steady influence may be observed : in 

 processes that are normal, and in those that are abnormal. The influ- 

 ence of reversion in the perpetuity of normal characters is fully recog- 

 nized, but the same can not be said of its true relation to those that are 

 abnormal. Writers who have treated upon this point apparently con- 

 sider the principle as one which tends to restore a lost character with- 

 out regard to its nature, or, in other terms, that a quality ill suited for 

 the continuance of life, and which has disappeared for one or more 

 generations, is quite as likely to reappear as one well suited. This 



