3 i8 THE POPULAR SCIENCE MONTHLY 



doubt that we are dealing with an inherited character. The great dif- 

 ferences in the length of life of an elephant and a mouse, of a parrot and 

 a pigeon, of a cicada and a squash bug, are as surely the result of in- 

 herited causes as are the differences in structure between those animals. 

 Within the same species different races or lines show characteristic dif- 

 ferences in length of life ; in the case of man the average length of life 

 is much greater in some families than in others, and life insurance com- 

 panies take account of this fact. Even within the same organism cer- 

 tain organs or cells are short-lived, whereas others are long-lived ; some 

 cells and organs live only through the early embryonic period, while 

 others live as long as the general organism. 



Obesity is another physiological character which may be inherited; 

 the members of certain families grow fat in spite of themselves, while 

 other families remain thin however well fed they may be. Here also 

 many factors enter into the result, but it seems probable that the dif- 

 ferentiating factor is a hereditary one. Baldness affects the male 

 members of certain families when they have reached a given age, while 

 in others neither care, dissipation nor age can rob a man of his bushy 

 top. Hemophilia, or excessive bleeding, after an injury, which is due 

 to a deficiency in the clotting power of the blood, is strongly inherited 

 in the male line in certain families. Fecundity and a tendency to bear 

 twins or triplets, left-handedness, a peculiar lack of resistance to certain 

 diseases, and many other physiological peculiarities 'are probably in- 

 herited. 



(d) Psychological characters appear to be inherited in the same 

 way that anatomical and physiological traits are; indeed all that has 

 been said regarding the correlation of morphological and physiological 

 characters applies also to psychological ones. No one doubts that par- 

 ticular instincts, aptitudes and capacities are inherited among both ani- 

 mals and men, nor that different races and species differ hereditarily in 

 psychological characteristics. Certain breeds of dogs such as the mastiff, 

 the bull dog, the terrier, the collie, and many others, are character- 

 ized by peculiarities of temperament, affection, intelligence and dispo- 

 sition. No one who has much studied the subject can doubt that dif- 

 ferent human races and families show characteristic differences in these 

 same respects. It is quite futile to argue that exceptional individuals 

 may be found in one race with the mental characteristics of another 

 race; the same could be said of different races of dogs, or of the sizes 

 of different races of beans or of paramecia. The fact is that racial char- 

 acteristics are not determined by exceptional and extreme individuals 

 but by the average or mean qualities of the race ; and measured in this 

 way there is no doubt that certain types of mind and disposition are 

 characteristic of certain families. 



There is no longer any question that some kinds of feeble-minded- 



