INTRODUCTORY 11 



of losing, or hesitating to accept, some tempting and plausible 

 theories. 



In the following pages, after a chapter upon the definition 

 and limitation of the term "internal secretion," it will be 

 desirable to treat first of the general methods of investigation 

 of the subject of internal secretion and the validity of the con- 

 clusions which may be drawn from results obtained by such 

 methods. Afterwards the internal secretion of glands which 

 have also an external secretion will be dealt with. These are 

 the liver, the pancreas, the kidney, the intestinal glands, and 

 the gastric glands. Following these, the internal secretion of 

 the testis and ovary (with its corpus luteum l ) will be described. 

 Then will follow in due order treatment of the function of the 

 " ductless glands " namely, the adrenal body, consisting of 

 "cortex" and "medulla"; the thyroid body; the para- 

 thyroid bodies ; the pituitary body, consisting of the " infundi- 

 bular " or " nervous " portion and the " glandular : portion ; 

 the thymus gland ; and the pineal body. 



Finally will be found a chapter dealing with the relation- 

 ships which exist between the various internally secreting 

 organs. 



1 The corpus luteum may be looked upon as a " ductless gland," but it 

 will obviously be convenient to treat of it along with the ovary (see p. 75). 



