200 DUCTLESS GLANDS 



that it checks for a time the development of the reproductive 

 organs. It is very large in a young child, but gradually reduces in 

 size during adolescence until it is very small in adults. The pineal 



body is at the base of the brain behind 

 ^.xyP\L^.tlixro{^ anc } above the pituitary. Extracts from 

 / A ^..\.thVmurs this gland do not have any observable 

 4^/1 L^a effect. There is some evidence, how- 



ever, that the injury or destruction of 



in a very young infant the thymus this gland in young children is usually 



followed by abnormal development. 



Beneath the diaphragm, behind and to the left of the stomach, 

 is the spleen. It increases in size after a meal and reaches its 

 maximum about five hours after digestion. Then it slowly 

 decreases to its former size. The cause of this activity is not 

 known. This gland possibly plays a part in the formation and 

 destruction of red corpuscles, because quantities of them are 

 found in it. If the spleen is removed from animals suffering from 

 one type of anaemia, splenic anaemia, beneficial results follow. 



The reproductive glands, also called the gonads, produce a secre- 

 tion that passes through a duct, and another secretion that is ab- 

 sorbed directly into the blood. Certain of the cells of these organs 

 make the sex cells which leave the glands through ducts. This 

 secretion is dealt with in a later chapter on reproduction. The 

 normal development of the body depends upon the internal secre- 

 tion of the sex glands. If the male sex glands or testes are re- 

 moved from young animals, it modifies the normal course of their 

 development. Thus we have the normal bull contrasted with the 

 modified ox and the normal stallion with the modified gelding. 

 Modified animals never acquire complete secondary sexual 

 characters. 



The secondary sexual characters in man include the beard, 

 and the large larynx which accounts for the deep voice. After 

 maturity has been attained, the changes that follow the loss of 



