METHOD OF ANALYSIS. 21 



The quantity of mucus in the mixed saliva must obviously be 

 liable to very great variations, according to the conditions under 

 which this fluid is collected. 



The ether-extract ranged from 5*8 to 9'6^ of the solid residue in 

 the cases in which I determined it in several analyses of my own saliva. 



In reference to the chemical qualitative and quantitative 

 analyses of the saliva, it may be generally observed that the same 

 principles and methods are applicable which have been described 

 in the first volume, in our remarks on the different animal sub- 

 stances ; hence we need here only refer to a few points which 

 require a special mode of treatment. In the first place the saliva 

 must always be filtered, in order to effect the removal of the 

 epithelial scales ; unfortunately, however, the saliva is often so 

 viscid and tenacious, that it undergoes decomposition before pass- 

 ing through the filter; indeed, it generally happens that the small 

 quantity of filtered and perfectly clear fluid begins to become turbid, 

 while the greater portion of the fluid still remains upon the filter. 

 In such cases it is often advisable to dilute the saliva with three 

 or four times its volume of boiling water ; and after the mixture 

 has been as thoroughly as possible cooled, and the mucous flocculi 

 for the most part deposited, to filter and proceed with the analysis; 

 but as in this case we are not able to separate the soluble from the 

 insoluble portion, it is better not to attempt the whole analysis, 

 since we should only obtain inaccurate results. We might cer- 

 tainly at once evaporate the viscid fluid, in order to extract the 

 residue with alcohol, ether, and finally with water ; but indepen- 

 dently of the circumstance that the aqueous extract is also difficult 

 of filtration, substances would be taken up by the alcohol and 

 ether, which do not pertain intrinsically to the saliva, but to the 

 epithelial cells, and to the fat and remains of food sometimes 

 mixed with them. 



It is obvious that if, before ^submitting the saliva to a chemical 

 analysis, we duly examine its morphological elements with the 

 microscope, we can ascertain whether the insoluble parts of the 

 saliva consist merely of epithelial cells and mucous corpuscles, or 

 whether they also contain fat, vibriones, or molecular granules of 

 an organic nature. In saliva which has been for a long time 

 exposed to the air, in morbid saliva, and especially when it exhibits 

 an acid reaction, such granules are of very frequent occurrence. 

 As substances for the most part in an actual state of change, they 

 do not fall within the domain of an accurate chemical analysis. 

 No one can confound mineral substances, as, for instance, crystals 

 of carbonate of lime, with these molecular granules. 



