PART II.-SPECIAL 



IN Part I, a brief account was given of the history of the 

 doctrine of internal secretion, of its physiological basis, and of 

 the general principles upon which the teaching is founded. In 

 Part II we propose to take the internal secretory organs separately 

 and to describe what is known of the nature and significance of 

 their activities. In the present state of our knowledge anything 

 in the nature of a systematic classification is impossible. The 

 only rational basis would be a morphological one, but this is 

 rendered impracticable by the insufficiency of the data at our 

 disposal. There is a general tendency to ascribe a specific activity 

 to every cell-form and to every kind of tissue, but though, in 

 a sense, we are justified in so doing, there is as yet no certain 

 proof of the internal secretory activity of the greater number 

 of cells and tissues. From the structure of a tissue we are, no 

 doubt, able to deduce its specific function, but we are a long 

 way from being able to infer the nature of its chemical correlative 

 function. 



There are also drawbacks to a classification upon purely 

 physiological grounds. In any such attempt organs and tissues 

 of the most dissimilar type would, on account of the similarity 

 of their function, be classed together; while organs possessing 

 activities in more than one direction w r ould be included in several 

 different groups. 



Such being the state of matters it is better to avoid all 

 attempts at classification and simply to give a list of the internal 

 secretory organs, taking them, as far as possible, in the order 

 of their importance. 



It is more in deference to custom than in support of any 

 personal conviction that the so-called " vascular " or " ductless ' 

 glands are first dealt with, leaving the second place to the other 

 internal secretory organs. The first group includes :- 



The organs of the thyroid apparatus, namely, the thyroid 

 gland and the parathyroid glands ; 



The thymus gland ; 



The two suprarenal systems, namely, the interrenal and the 

 adrenal, together with the carotid and coccygeal glands; 



The hypophysis cerebri or pituitary gland, consisting of the 

 anterior and posterior portions, together with the pineal gland. 



The spleen, which was formerly considered a vascular gland, 

 is now regarded as essentially haematopoietic in its activity, its 

 internal secretion having no great physiological significance. 



The second group includes : 



