174 CHEMICAL CORRELATION 



that are exhibited in shows owe their exceptional size to 

 ovTr-activity of this phmd during the normal growth 

 period of childhood. The contrary condition of dwarf- 

 ishness is thought to be the result of under-activity of 

 the gland. 



The Interstitial Hormone. — Intermingled with the 

 strictly reprockictive parts of the organs of reproduction 

 are cells which are glan(hilar in function and to which 

 have been given the name of interstitial gland cells. The 

 hormone which they secrete is of particular importance 

 in growth, particularly in that stage which is concerned 

 with the change from youthfulness to maturity. There 

 are certain bodily changes characteristic of this period 

 consisting in the development of the so-called " secondary 

 sexual characters. " Among them are included such 

 changes as the alteration of the vocal cords which causes 

 the voice to break, and the development of hair on the 

 face. The hormone of the interstitial gland is of special 

 interest because observation of its effects first suggested 

 the idea of chemical correlation. Although castration of 

 domestic animals and caponization of fowls had been 

 practiced for centuries and their effects upon the develop- 

 ment of the secondary sexual characters had become a 

 matter of everyday knowledge, it remained for the biolo- 

 gist, about the middle of the last century, to explain the 

 connection. From the studies thus initiated came others 

 which have given us all that is now known about the 

 hormone mechanism. 



Hormones Affecting Functional Metabolism. — 

 Although, as already pointed out, functional metabolism 

 in animals is for the most part under nervous rather than 

 chemical control, there are some instances in which the 

 functional metabolism is affected by hormones, so this 

 typo of regulation cannot be altogether neglected. 



The Pancreatic Hormone. — The pancreas is prima- 

 rily an organ for the manufacture of a digestive secretion 

 which is poured out into the intestine through a duct; 



