378 C. G. Mitscherlich on [May 



Gmelin was greatly underrated, because they employed a 

 fluid which was produced by the stimulus of tobacco smoke, 

 and was mixed with the secretion of the mucus membrane 

 of the mouth. 



Action of re-agents. — Saliva from the fistula was not 

 quite clear, for it contained some white flocks, which after 

 standing for some time sunk to the bottom of the vessel, 

 and were then separated in greater abundance from the fluid. 

 This first substance does not appear to belong to the saliva, 

 but seems to be derived from the mucus membrane of the 

 parotid gland and duct, as well as from the peculiar 

 membrane of the fistula. When the saliva is filtered this 

 substance remains on the filter. 29*797 grms. (458*8 grs.) 

 of fresh saliva are mixed with 0*0015 grm. (*023 gr.) of the 

 matter: 24*955 grms. (384*2 grs.) gave in another trial 0*019 

 grm. (0*29 gr.) This substance is insoluble in water, 

 alcohol and acids, dissolves in potash, out of which solution 

 it is precipitated by acids, and has when dried a brown 

 colour. Its chemical properties seem to indicate, that it is 

 not chemically combined with the saliva, but mechanically 

 mixed with that fluid. 



The filtered saliva is quite clear ; more or less of a yel- 

 lowish colour ; not mucilaginous ; alkaline and of the density 

 already given. After standing for some time, a whitish 

 mucus like substance separates which is insoluble in water, 

 alcohol and acids, dissolves easily in potash, and is partly 

 precipitated out of this solution by acids. This substance 

 will be noticed in the sequel. 



Alcohol produces in pure saliva a white precipitate, 

 which by heating is partly dissolved, but on cooling again 

 falls down. 



The precipitate with nitrate of silver is easily soluble in 

 ammonia. 



Tincture of galls occasions a clear brown precipitate, 

 which dissolves by the application of heat, but re-dissolves 

 when the liquid is allowed to cool. 



Acetate of lead forms a copious white precipitate which 

 does not dissolve by heating, but disappears by an excess 

 of acetic acid. 



Sulphuric acid gives a slight flocky precipitate ; caustic 

 potash and ammonia produce no visible effect. 



Quantitative analysis. — The quantity of free alkali was 



