

144 DIGESTION. 



much more viscid than either of the other secretions ; so much so, that 

 it cannot be poured out in drops when received in a glass vessel, but 

 adheres strongly to the surface of the glass. All the salivary secretions 

 are alkaline in reaction. 



We have obtained the parotid saliva of the human subject in a state 

 of purity by introducing directly into the orifice of Steno's duct a 

 silver canula a little over one millimetre in diameter. The other ex- 

 tremity of the canula projects from the mouth between the lips, and 

 the saliva is collected as it runs from the open orifice. This method 

 gives results much more valuable than observations made on salivary 

 fistulae and the like, since the secretion is obtained under perfectly 

 healthy conditions, and unmixed with other animal fluids. 



The result of many different observations, conducted in the manner 

 above described, is that the human parotid saliva, like that of the dog, 

 is colorless, watery, and distinctly alkaline in reaction. It differs from 

 the mixed saliva of the mouth, in being perfectly clear, without tur- 

 bidity or opalescence. Its flow is scanty while the cheeks and jaws 

 remain at rest ; but as soon as the movements of mastication are excited 

 by the introduction of food, it runs in much greater abundance. We 

 have collected, in this way, from the parotid duct of one side only, in a 

 healthy man, 31.1 grammes of saliva in the course of twenty minutes ; 

 and in seven successive observations, made on different days, comprising 

 in all three hours and nine minutes, we have collected a little over 194 

 grammes. 



The parotid saliva obtained in this way has been analyzed by Prof. 

 Maurice Perkins, with the following result : 



COMPOSITION OF HUMAN PAROTID SALIVA. 



Water 983.308 



Organic matter precipitable by alcohol .... 7.352 

 Substance destructible by heat, but not precipitated by alcohol 4.810 



Sodium sulphocyanide 0.330 



Lime phosphate 0.240 



Potassium chloride 0.900 



Sodium chloride and carbonate . 3.060 



1000.000 



Prof. Perkins found, in accordance with our own observations, that 

 the fresh parotid saliva, when treated with iron chloride, showed no 

 evidences of sulphocyanogen ; but after the organic matters had been 

 precipitated by alcohol, the filtered fluid was found to contain an appre- 

 ciable quantity of sulphocyanide. 



The parotid saliva, accordingly, differs from the mixed saliva of the 

 mouth in containing some substance which masks the reaction of sul- 

 phocyanogen. If the parotid saliva and that from the mouth be drawn 

 from the same person within the same hour, the addition of iron chloride 

 will produce a distinct red color in the latter, while no such change 

 takes place in the former. And yet the parotid saliva itself contains a 



