1835.] Human Saliva. 383 



Acetate of lead forms a white precipitate which does not 

 disappear on the addition of water, and is not dissolved by 

 acetic acid. 



Nitrate of silver produces a precipitate readily soluble in 

 ammonia. 



By exposure to a strong heat it affords the product of ani- 

 mal matter, and a carbonaceous substance is left containing 

 potash and soda. It follows, from these experiments, that 

 the substance is identical with the salivary matter, and be- 

 comes soluble in alcohol of 0*863, by combining with 

 extractive matter. 



The substance soluble in water and absolute alcohol has 

 a yellowish red colour; affords by calcination the same 

 products as other animal substances, and leaves a salt which 

 dissolves in dilute muriatic acid. This salt, when treated 

 with chloride of platinum and absolute alcohol, partly 

 precipitates and partly dissolves, affording in the usual way 

 potash and soda. The properties of this substance can be 

 best observed when the saliva has been neutralized with 

 sulphuric acid, as the extract then contains no dissolved 

 salt. As much water is now to be added as is requisite for 

 the solution of the animal matter, when the crystallized 

 salt dissolves first. The liquid is then decanted from the 

 crystallized salt, and on the addition of muriate of barytes 

 no sulphuric acid can be detected. 



This liquid animal substance readily soluble in alcohol 

 and water has a red colour; possesses an acid reaction 

 without containing sulphuric acid, (perhaps lactic acid, 

 which may be obtained in a free state by the addition of 

 sulphuric acid,) and produces no precipitate with acids, 

 potash, ammonia and corrosive sublimate. Acetate of lead 

 produces a considerable white precipitate which dissolves 

 by boiling. Muriate of iron affords a flocky reddish preci- 

 tate, which does not re-dissolve by adding water. 



A precipitation proceeds from the addition of nitrate 

 of silver, which completely disappears by the action of 

 ammonia. 



The results of the preceding experiments may be summed 

 up as follows : 



1. The separation of the saliva ceases when the muscles 

 and tongue are motionless, and by the absence of the usual 

 nervous stimulus. 



