MORBID HEREDITY. 397 



generates of different origin a similarity that permits us to make 

 a classification the scale of which is as a whole narrow enough, 

 has been reproduced in experiments having the provocation of 

 artificial monsters as their object. If the incubation of hen's 

 eggs is disturbed by eccentricities of temperature, if they are 

 warmed too much or not enough, if they are deprived of air, if 

 poisonous substances or substances capable of modifying the 

 nutrition of the embryo ether, chloroform, alcohol, essences, 

 or nicotine are introduced into the medium in which they 

 respire, if the same substances are caused to penetrate into the 

 albumen, if they are shaken by abrupt shocks or feeble but re- 

 peated blows, monstrosities are generally produced ; but it does 

 not appear that any of these causes will provoke exclusively the 

 formation of a special monstrosity. Each of these causes will 

 produce a variety of deformities, any of which may resemble 

 other deformities produced by other causes. In short, the gen- 

 eral facts already noticed in degenerating descent may be found 

 in hatches experimentally disturbed unlikeness in the same 

 families and resemblance of unlike types of one family with 

 those of another. 



Besides resulting in ultimate sterility, morbid heredity and 

 degeneration contribute to the destruction of families and races 

 by producing mental and moral differences among them that lead 

 to dissensions and conflicts as mischievous as diseases. When 

 multiple crossings of normal individuals have been effected in a 

 single locality or country, they create in the end both physical 

 resemblances a family air, a national type and also psychical 

 likenesses, which entrain a community of tastes and consequently 

 of moral ideas susceptible of becoming fixed for a long series of 

 generations and of constituting a family or national character. 

 The dissolution of heredity, which may be realized either by the 

 introduction of strangers of too different races, or under the 

 influence of native causes of degeneration, is marked both by 

 physical unlikenesses and by the psychical and moral ones that 

 necessarily accompany them. The social discords that spring up 

 among a people like those that so often divide the families of 

 degenerates, taken together, constitute a manifestation of the dis- 

 solution of heredity ; their source is in a biological fact. 



The facts that authorize us to regard morbid heredity or de- 

 generation in general as the consequence of disorders of nutrition 

 during the developmental period of evolution permit us to com- 

 prehend the exceptions to the laws of heredity, and consequently 

 to conceive the possibility of securing means of favoring these 

 exceptions and of contending against degeneration. 



A strong temptation arises to propose a law prohibiting the 

 marriage of certain categories of degenerates, whereby the natural 



