76 



THE ORIGIN AND EVOLUTION OF LIFE 



It has also been discovered that the source of such internal 

 secretions is not confined to the ductless glands, but that cer- 

 tain duct-glands, such as the ovaries, testes, and pancreas, 

 serve a double function, for they secrete not only through 

 their ducts, but they also produce an internal secretion 

 which enters the circulation of the blood. It is, of course, a 

 fact known from remote antiquity that removal of the sex 



Fig. io. Hantd Form Determined by Heredity (.4) and by Abnormal Internal 



Secretions (B, C). 



A. Hereditary brachydaclyly (partial) attributed to congenital causes. After Drinkwater. 



B. Acquired brachydactyly. This abnormally broad and stumpy hand shows one of the 



results of abnormally excessive secretions of the pituitary gland. After Gushing. 



C. Acquired dolichodactyly. This slender hand with tapering fingers shows one of the 



results of abnormally insufficient secretions of the pituitary gland. After Gushing. 



glands from a young animal of either sex not only inhibits the 

 development of all the so-called secondary sexual characters, 

 but favors the development of characters of the opposite sex. 

 During the last and present centuries it has been discovered 

 that all these inhibited characters may be restored by success- 

 fully transplanting or grafting into some part of the body the 

 ovary or testicle, either from the same or another individual, 

 thus proving that in both sexes the secondary sexual characters 



