1813.] Chemical Properties of Animal Fluids. 207 



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 properties 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 analyzed, 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, consist- 

 ing, as has been already shown, of the muriates of potash and 

 soda, of lactate of soda, and of an extractive animal substance 

 precipitable by tannin : and secondly, of a portion soluble only 

 in water, containing soda (which acquires carbonic acid by eva- 

 poration, 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 by muriate of mercury. Some- 

 times 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 the lactic, and in the urine this is 

 mixed with the uric acid. Urine seems to contain only a single 

 peculiar characteristic matter ; but milk has as many as three, 

 namely, butter, curd, and sugar of milk, which, however, seem 

 to be produced by different organs that mingle their fluids in the 

 same receptacle. The perspired fluid appears to have no peculiar 

 matter, but to be a very watery liquid with hardly a vestige of 

 the albumen of the blood, and, in short, is the same as the 

 other excretory fluids would be when deprived of their peculiar 

 matter. If we suppose this matter taken away from those excre- 

 tions that possess it, the remaining fluid would be found to have 

 properties very different from the fluid part of the secretions, 

 when equally freed from their peculiar matter. That of the 

 excretions is acid, contains earthy phosphates, and when evapo- 

 rated leaves a much larger residue than the fluid of the secre- 

 tions. This residue is yellowish brown, of the consistence of 

 syrup, with an unpleasant sharp saline taste of the salts that it 

 contains. It reddens litmus, is mostly soluble in alcohol, and 

 this spirituoussolution contains the muriates of the blood together 

 with free lactic acid, much lactate of soda (the soda being the 

 free alkali of the blood neutralized by this acid) and the extractive 

 matter which always accompanies this neutral salt. The part 



