SECTION X 



INTERNAL SECRETIONS THEIR PRODUCTION 

 AND ACTION 



THE products of the metabolism of the various organs 

 are carried away in the lymph and blood, and certain of 

 these products exercise an important influence upon other 

 structures in the body. These products have been termed 

 Internal Secretions, and the mode of action of some of 

 them has been more or less investigated. Much, however, 

 remains to be done before our knowledge can be deemed 

 anything like satisfactory. 



Among the structures which are known to yield such 

 active internal secretions are the following : 



1. Suprarenal Bodies. These structures lie just above 

 the kidneys. Each consists of a tough cortex composed 

 of epithelial-like cells arranged in columns, and a soft 

 medulla consisting of cells derived from neuron cells 

 which stain of a peculiar brown colour with chromic acid. 

 The medulla is developed from the sympathetic chain of 

 ganglia. The cortex is a perfectly independent structure 

 derived from the surrounding mesoblast, and in teleostean 

 fishes it is quite apart from the representative of the medul- 

 lary part. A suprarenal body is thus two distinct and 

 independent organs combined with one another (Fig. 151). 



Long ago Brown-Sequard stated that removal of these 

 bodies causes great muscular weakness, loss of tone of the 

 vascular system, loss of appetite, and finally death in a short 

 time. Addison had already pointed out that a similar set 

 of symptoms, accompanied by pigmentation of the skin, is 

 associated with diseased conditions of these organs in man. 

 Within the last few years it has been demonstrated that in- 

 jections of small quantities of the medullary portion of the 



bodies have a powerful effect on the muscular system gene- 



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