THE CIRCULATION OF THE BLOOD 189 



the liver, increasing the output of glycogen into the blood, and it 

 interferes with the secretions and contractions of the stomach. The 

 adrenin, as this substance is called, also hastens the clotting of blood. 



In young mammals there is a soft organ lying in the front part of 

 the chest, the thymus, the ferments from which have an important 

 influence on the growth of the animal. Another ferment that affects 

 the growth is absorbed by the blood from a little body lying at the 

 base of the brain. 



These various ferments are sometimes called internal secretions, 

 because they are absorbed from inside the organ, instead of coming 

 out of the gland through special ducts, as is the case with ordinary 

 glands. 



