Introduction. 



mother. Girou de Buzareingues, in his work De la Generation, 

 containing some curious facts observed by him, tells us that he 

 knew two brothers who in early life resembled their mother, while 

 their sister resembled the father. These resemblances were such as 

 to strike all who saw them. ' But now, ' says he, ' and ever since 

 their youth, the two boys resemble the father, while the daughter 

 has ceased to be like him/ This same author was led, in conse- 

 quence of numerous observations, to believe that changes of this 

 kind are more frequent and more thorough in the case of boys 

 than in that of girls. 



The system of intentional and conscious selection has been 

 applied even to man. Frederick William I., the father of Fred- 

 erick the Great, who was noted for his love of colossal men, dealt 

 with his regiment of giants as stock-breeders deal with their 

 cattle. He would not allow his guards to marry women of stature 

 inferior to their own. Haller used to boast of his * belonging to 

 one of those races whose members, by reason of their imposing 

 stature, seem born to rule other men.' 



Heredity may be also traced in all that concerns the com- 

 plexion of the skin, and the shape and size of the body. Thus, 

 so truly is ooesity the result of an organic predisposition, that it 

 has often been known to make its appearance amid privations, 

 and under all the disadvantages of hard labour and poverty. 



Heredity influences the internal conformation no less than 

 the external structure. Nothing is more undismited than the 

 heredity of the form, size, and anomalies of the osiers system ; 

 and universal everyday experience proves the heredity of all the 

 proportions of the cranium, thorax, pelvis, vertebral column, and 

 the smallest bones of the skeleton. Even the heredity of excess 

 or defect in the number of the vertebrae and the teeth has been 

 ascertained. (Lucas.) The circulatory, digestive, and muscular 

 systems obey the same laws which govern the transmission of the 

 other internal systems of the organism. There are some families 

 in which the heart and the size of the principal blood-vessels are 

 naturally very large ; others in which they are comparatively small ; 

 and others, again, which present identical faults of conform- 

 ation. Lastly and this is a point that more nearly concerns us < 

 heredity regulates the proportions of the nervous system. It is 



