URINE. 123 



acid. And although processes of transposition take place in 

 the healthy animal body, rendering insoluble substances soluble 

 in the stomach and bowels, yet these processes are of a different 

 kind from that process of putrefaction of casein in milk which 

 causes the formation of lactic acid. 



" Direct experiments prove that fresh urine, of a strongly 

 acid reaction, and taken from various healthy individuals, when 

 cautiously neutralized with baryta water, does not retain in so- 

 lution the least detectable trace of baryta. Now, as lactate of 

 baryta is readily soluble in water, the urine would certainly, and 

 of necessity, contain baryta, if its acid reaction were really owing 

 to the presence of lactic acid. Upon the addition of the very 

 first drop of the baryta water to urine an extremely copious pre- 

 cipitate is formed; this precipitate contains urate and phosphate 

 of baryta and of lime, but no detectible trace of baryta is found, 

 even although only just so much baryta water is added as to 

 leave the urine still possessing a feebly acid reaction. 



" Carbonate of magnesia and calcined magnesia act upon 

 urine in precisely the same manner. If either of these sub- 

 stances be mixed with water, so as to form a milky fluid, and be 

 then added to urine with an acid reaction, the acid reaction 

 will immediately cease, and a very considerable white precipi- 

 tate be formed. The fluid now manifests a feebly alkaline re- 

 action, and contains a trace of magnesia in solution. It is a 

 remarkable circumstance that magnesia withdraws the phos- 

 phoric acid from the urine so completely, that a mixture of per- 

 chloride of iron and acetate of potash no longer indicates a trace 

 of phosphoric acid in the urine which has thus been treated with 

 magnesia. 



" Had lactic acid been the solvent of the lime and magnesia 

 present in the urine, one would have expected that a corre- 

 sponding amount of baryta, or of magnesia, would have taken 

 its place upon its separation. But, as I have already observed) 

 not a trace of baryta is found in solution when that substance 

 has been employed for neutralizing the acid, and only a slight 

 trace of magnesia when it has been used for the same purpose. 



" But as urine contains a certain amount of alkaline phos- 

 phates, i. e. phosphate of soda and phosphate of potash, and as 

 baryta and magnesia form, with phosphoric acid, insoluble 



