INTRODUCTORY 15 



easy. We have but to toil awhile, endure awhile, 

 believe always, and never turn back." 



Schafer's definition of an endocrine gland seems 

 to be as accurate as possible. " Material which 

 is passed into the blood or lymph from any tissue 

 or organ of the body forms its internal secretion, 

 and organs which are not known to possess any 

 other functions than that of passing such material 

 into the blood or lymph are internally secreting 

 or endocrine organs." 



This term is not usually extended to the 

 lymphatic glands. Strictly speaking, then, we 

 must consider the thyroid, para-thyroid group, 

 the suprarenals, medullary and cortical, the 

 pituitary gland, anterior and posterior, the pineal 

 and the internal secretory part of the pancreas as 

 the endocrine glands with which we have to deal. 



The testes, the ovaries, and the thymus all 

 come nearly into the same category, but not 

 entirely ; they can all, however, be harnessed for 

 our work. With one or two exceptions the in- 

 ternal secretion is a matter of surmise only, but 

 the evidence from the physiological side and from 

 the clinical is so strong that doubt vanishes ; 

 the most sceptical must allow that we have at 

 least a good working hypothesis and one bearing 

 good fruit. 



