CHAPTER IV. 

 SECRETION. 



Secretion and Excretion. Ordinarily the product of glan- 

 dular activity is spoken of as a secretion. On the one hand, 

 glands may take from the blood substances which are preformed 

 in that fluid, which would accumulate and produce detrimental 

 effects if not removed, and which are discharged from the body. 

 On the other hand, glands may form out of materials furnished 

 by the blood substances which are peculiar to that gland's activ- 

 ity, which have an office to perform in the economy, which do not 

 accumulate on removal of the gland, and which are not dis- 

 charged from the body. The product in the first case is an 

 excretion, in the second case a secretion. But when it comes 

 to naming an exclusively excretory or an exclusively secretory 

 gland, the task is found to be practically impossible. Probably 

 the most typical excretion of the body is the urine, yet there 

 are in the urine substances, like hippuric acid, etc., which are 

 undoubtedly formed by the kidney, and which do not preexist in 

 the blood. The succus entericus, e. g., would seem as typical a 

 secretion as it is possible to find, but not infrequently it contains 

 urea when the activity of the kidney is impaired, to say nothing, 

 under normal conditions, of the water and salts which are taken 

 as such from the blood. The liver is notable in its secreto- 

 excrementitious action. While the desirability of thus separat- 

 ing the glands into secretory and excretory and their products 

 into secretions and excretions is granted, the impossibility of 

 such a division is apparent. 



It is possible in most cases to apply the distinction to the 

 separate constituents of the product of a particular gland, but 



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