HEREDITY. 343 



sary to admit that a fragment of the germinative j)lasma of the 

 ancestor has been preserved, latent for years, perhaps even for cen- 

 turies, until the day when by reason of favorable circumstances this 

 fragment succeeds in becoming isolated in a gamete and in becoming 

 predominant, so as to reproduce the ancestral form. The matter is 

 much more simple than that. There is no latent ancestral frag- 

 ment; there is nothing that represents am^ of such ancestors in a 

 germinative plasma any more than there is in carbonic acid and 

 lime any representative of the limestone from which they were for- 

 merly extracted. If the ancestor reappears under certain circum- 

 stances, which one can reproduce at will, it is because the union 

 of two different germinative plasmas has formed a combination 

 entirely identical with the germinative plasma of the ancestor in 

 the same way that by uniting carbonic acid and lime we succeed in 

 re-forming limestone. 



The interest of these studies of heredity is not confined to pure 

 science alone. Heredity as a factor has such considerable importance 

 in history, in sociology, in our own personal development, that it may 

 often be of use to us to understand its laws. We may, to a certain 

 degree, predict our own future and that of our children, and as this 

 is only a jjrediction of probabilities there can })e nothing unreasonable 

 in doing it. If the prevision is disagreeable, there is always the hope 

 remaining that a favprable probability may intervene. 



For example, there is no doubt that the duration of life, depending 

 as it does upon the structure of our organism, is markedly hereditarj^ 

 We may cite the case of Turgot, who at 50 years of age put his affairs 

 in order, although he was in vigorous health, knowing that in his 

 famil}' the fiftieth year was rarely exceeded. He died at 53. Cen- 

 tenarians invariably have had parents of great age. It must, of 

 course, be understood that such transmission of the duration of life 

 is merely a probability, and also that it rests upon the condition that 

 our mode of life is fairly analogous to that of our ancestors. Natu- 

 rally an accident or a contagious disease may cause death before the 

 time fixed by heredity, but this is not the fault of the latter. 



It is possible that certain diseases, or, to be more exact, certain 

 diatheses or morbid tendencies follow in their heredity the laws of 

 Mendel, so it is said that cancer is hereditary in the proportion of 

 1 to G or 9. It is then quite probable that there is in the gametes a 

 disjunction between the normal state and this pathological character. 

 I will cite a celebrated example of its transmission: Charles Bona- 

 parte, the father of Napoleon, died at the age of 39 of cancer of the 

 stomach. Among his eight children one alone. Napoleon, was stricken 

 with the same disease when 50 years of age. 



In the same family there is a fine example of dominance. The 



