CHAPTER XV. 



THE ENDOCRINE GLANDS. 



It is known that the nervous system controls integration of 

 bodily acti\ities so that there is a harmonious functioning of the 

 organ systems making possible successful adjustments to changes 

 in the external world. In addition, an important part of the uni- 

 fying and coordinating function is effected by the system of chemical 

 coordinators, the endocrine gland secretions. 



The secretion products of exocrine glands, as already described, 

 collect in ducts. Endocrine glands, on the contrary, have no excre- 

 tory duct systems. Their secretions pass into the blood or lymph 

 vessels and thus enter the circulation stream for distribution to 

 various organs and svstems. 



Pineal gland 



Adrenal 



Gonad 



Pitiiilary 



Pancreai 



Fig. 155. — Diagram showing the location of ondoorine glands. 



An endocrine gland may be defined as one that secretes into the 

 })]o()d stream some hormone or chemical sul)stance which stimulates 

 or depresses the physiological activity of other groups of cells, thus 

 affecting growth, development, and the general condition of the 

 body as a whole. Secretion of one gland may affect the activity or 

 effect of the secretion of some other endocrine gland, i. e., they 

 are physiologically interrelated. 



