PAROTID SALIVA. 13 



expelled from its combination with non-acid organic substances by 

 the very weakest acids, and as for instance even carbonic acid. 

 Frerichs* found that 100 grammes of saliva, secreted by a man 

 smoking tobacco, were neutralized by 0*150 of a gramme of sul- 

 phuric acid. 



According to Wright, the quantity of alkali in the saliva is in- 

 creased after the use of fatty, aromatic, acid, spirituous, and more 

 particularly indigestible kinds of food and drink. 



In attempting to collect pure human saliva, we must avoid the 

 use of irritants such as tobacco, either smoked or chewed, or 

 aromatics which, although they increase the secretion, become 

 mixed with it, and render it comparatively unfit for examination. 

 The simplest method of collecting a large quantity of saliva in a 

 short time, is by exerting strong pressure under the chin, and at 

 the same time tickling the palate with a feather; a feeling of 

 strangulation rapidly ensues, during which the saliva is ejected 

 from the mouth. The best method of collecting the saliva of 

 animals, is by presenting them with their favourite food after they 

 have been kept for sometime fasting ; the secretion flows freely on 

 pressing the nostrils in a backward direction. 



The method which Magendie and Lassaigne adopted for the 

 purpose of collecting the mixed saliva of animals, namely, cutting 

 into the oesophagus, cannot be avoided for certain experiments, 

 but, for ordinary purposes, it is not only cruel and indirect, but also 

 unphysiological ; for how can we expect, that after such an inroad 

 on animal life as must arise from the exposure and opening of the 

 oesophagus, a secretion can remain in its normal state 2 



We have already mentioned that ordinary saliva is a mixture of 

 the secretion of the buccal mucous membrane and of several 

 glands ; we now proceed to notice these secretions individually. 



PAROTID SALIVA has hitherto only been accurately examined 

 in man by Mitscherlichf and Van Setten ; the parotid secretion 

 of horses and dogs has, however, very often been analysed. It is 

 usually perfectly limpid and colourless, devoid of smell and taste, 

 incapable of being drawn out in threads, and of a distinctly 

 alkaline reaction. In a male patient, Mitscherlich found that the 

 specific gravity varied from 1-0061 to 1'0088 ; in dogs it was found 

 by Jacubowitsch to vary from 1'0040 to 1-0047; and in horses I 

 found it to range from 1-0051 to 1*0074. 



* Wagner's Handworterb. d. Physiol. Bd. 3, Abt. 1, S. 760. 



t Op. cit. 



$ De Saliva ejusque vi ut utilitate. Groning. 1837. 



