258 SECRETION. 



of water as the blood, so that the change induced by the nervous 

 influence seems to be confined to that of altering the chemical 

 form of the albuminous materials 6 , without affecting their rela- 

 tive proportion to the water and other substances dissolved in the 

 blood. The bile, spermatic fluid, &c. are of this kind. The latter 

 species consists of fluids, in which the influence of the nervous 

 system has separated a large portion of the albuminous matter, 

 and left the remaining liquid proportionally watery. The saliva, 

 the humours of the eye, and the effused serum of membranes 

 are of this species ; and in these the quantity of salts, and in ge- 

 neral also of alkali, is the same as in the blood. 



" The influence of the chemical agent of secretion is, there- 

 fore, chiefly spent upon the albuminous materials of the blood, 

 which seem to be the source of every substance that peculiarly 

 characterises each secretion, each of which is sui generis, and is 

 its principal constituent. All the other parts of the secretion 

 seem to be rather accidental, and to be found there only because 

 they were contained in the blood out of which the secretion was 

 formed. Therefore, in examining the secreted fluids, the chief 

 attention should be paid to the peculiar matter of the fluid, which 

 varies in all. This matter sometimes retains some of the pro- 

 perties of albumen; at other times, none; and hence an accurate 

 analysis, showing the quantity and nature of this peculiar matter, 

 is above all to be desired. 



" If the several secretions be supposed to be deprived of their 

 peculiar matter, and the remainders analysed, the same residue 

 would be found from them all, which also would be identical 

 with the fluid separated from the serum after its coagulation. 

 Thus we should find, first, a portion soluble in alcohol, consisting 

 of the muriates of potash and soda, lactate of soda, and of an 

 extractive animal substance, precipitable by tannin ; and, se- 

 condly, of a portion soluble only in water, containing soda (which 

 acquires carbonic acid by evaporation, and is separable by acetic 

 acid and alcohol) and another animal substance, not extract, 

 precipitable from its solution in cold water, both by tannin and 

 muriate of mercury. Sometimes a vestige of phosphate of soda 

 will also be detected. 



" The excretions are of a more compound nature. They all 

 contain a free acid, which is termed lactic, and in the urine this 



c This appellation Berzelius gives to the fibrin, albumen, and colouring matter 

 of the blood. 



