The Laws of Heredity. 145 



individual characteristics. Hence the evident conclusion that 

 heredity is the law, non-heredity the exception. Suppose a father 

 and mother both large, strong, healthy, active and intelligent 

 produce a son and a daughter possessing the opposite qualities. 

 In this instance, wherein heredity seems completely set aside, it 

 still holds good that the differences between parents and children 

 are but slight, as compared with the resemblances. 



Let it not be said that we have dwelt too long on points that 

 are self-evident They are so clear that we forget them, and argue 

 only from isolated cases, thus changing the state of the question 

 by the way in which it is stated. But when, on the contrary, we 

 consider the facts as a whole, heredity appears universal, and we 

 are less surprised at rinding characteristics that are hereditary, than 

 in finding those which are not 



CHAPTER II. 



THE LAWS OF HEREDITY. 



THUS, then, heredity presents itself to us as a biological law, 

 that is, inherent in every living thing, having no other limits than 

 those of life itself. Life under all its forms vegetal, animal and 

 human, normal and morbid, physical and mental is governed by 

 this law. It is, in fact, concerned with the essential and inmost 

 nature of vital activity. Among the various functions which in 

 their united action constitute life, two are primary the one, nutri- 

 tion, which preserves the individual, the other, generation, which 

 perpetuates the species. Some physiologists even reduce these to 

 one, nutrition being, in their view, only a form of generation, or in 

 the words of Claude Bernard, 'a continuous creation of organized 

 matter by means of the histogenic processes appertaining to the 

 living creature.' Ultimately, therefore, the vital functions are 

 reduced to generation ; and as it is from this that heredity 

 immediately flows, we must conclude that the law of hereditary 

 transmission has its rise in the sources of life itself. 



If we accept the foregoing views, the law of heredity would seem 

 to be one of absolute simplicity. Like produces like : the progeni- 

 tor is repeated in the descendant. Thus the primitive types would 



