SALIVA. 3 



ther with the phosphates and carbonates of lime and magnesia. 

 According to Hiinefeld, ammoniacal salts are also present. On 

 evaporating the saliva, we obtain a brown residue, which evolves 

 a rather agreeable odour, resembling that of toasted bread. 



In certain pathological states the saliva contains other sub- 

 stances besides those already enumerated : thus, in one case of 

 morbid saliva I detected free acetic acid, and in another I found 

 a considerable quantity of a substance resembling casein. 



The albumen contained in the saliva is indicated by the 

 turbidity produced on the application of heat ; and after the 

 removal of the coagulated albumen by nitration, the presence 

 of the various extractive matters may be shown by the precipi- 

 tates thrown down by acetate of lead, bichloride of mercury, 

 and tannin ; the casein may be indicated by the addition of 

 acetic acid ; ptyalin, and probably casein, by the addition of 

 alcohol to clear and somewhat concentrated saliva ; and sulpho- 

 cyanogen, by the redness produced on the addition of perchlo- 

 ride of iron. 



With a view to separate the constituents of the saliva I eva- 

 porated a known quantity to dryness, and thus determined the 

 water. I then treated the residue with ether, for the purpose 

 of extracting the fat ; and with water, in order to take up the 

 ptyalin, extractive matters, and salts. The insoluble residue 

 that had resisted the action of ether and water, consisted of 

 albumen and mucus. Another portion of the saliva was de- 

 canted from its precipitate, evaporated to a small residue, and 

 the ptyalin, with a trace of extractive matter, precipitated by 

 alcohol. When the saliva contains a caseous matter, (which 

 I have observed in large quantity in the saliva of the horse,) 

 the precipitate of ptyalin and casein produced by the alcohol 

 must be dissolved in water, and the casein then thrown down 

 by the careful addition of acetic acid. In this case, a portion 

 of the casein precipitated by the alcohol usually remains un- 

 dissolved by the water. I have detected free acetic acid in the 

 saliva discharged during salivation. In order to determine its 

 quantity, the saliva must be accurately neutralized by a solu- 

 tion of carbonate of potash of known strength ; from the amount 

 of the alkaline solution required, the quantity of acetic acid 

 can be calculated. If, in addition to acetic acid, free lactic acid 

 is likewise present, the residue of the saliva, after evaporation, 



