255 



CHAP. XV. 



SECRETION. 



" BESIDES the products of nutrition, fluids of extremely various 

 descriptions are^ produced from the blood by means of secretion, 

 which Haller, no less than his predecessors, with truth and regret 

 declared to be among the most obscure parts of physiology." * 

 While nutrition is the production of the component solids from the 

 blood, secretion is thus the production of fluids from it, by vital 

 processes. The nature of the process in both must be the same. 

 The solid products of nutrition are also said by many to be first 

 deposited in a fluid state. 



" The secreted fluids differ, on the one hand, so considerably 

 among themselves, and, on the other, have so many points of 

 resemblance, that their classification cannot but be extremely 

 arbitrary. If we arrange them according to the degree of differ- 

 ence between them and the blood from which they are formed, 

 they will stand in the following order : 



" First, the milk, which may be in some degree considered as 

 chyle reproduced, and appears formed by the most simple process 

 from the blood newly supplied with chyle. 



" Next, the aqueous fluids, as they are commonly denominated 

 from their limpid tenuity, although the greater part differ im- 

 portantly from water in the nature of their constituents, and 

 especially in the proportion of albumen : such are the humours 

 of the eye, the tears, in all probability the vapour contained in 

 the cellular interstices and the cavities of the abdomen and 

 thorax ; nearly similar, also, is the fluid of the pericardium and 

 of the ventricles of the brain." They contain mucus, soda, 

 hydrochlorates, and phosphates. 



a " Fouquet on Secretion, in the Encyclopedical Dictionary of Paris, t. xir. 

 Fr. L. Kreysig, De secrelionibus. Sp. i. ii. Lips. 1794. sq. 4to. 

 Ignat. Dollinger, Was ist dbsonderung, und wie Gesckieht sie ? Herbipol- 

 1819. 8vo." 



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