126 DIGESTION. 



The result of many different observations, conducted in this way, 

 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 any turbidity 

 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, 480 grains 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 3000 grains. 



The parotid saliva obtained in this way has been analyzed by 

 Mr. Maurice Perkins, Assistant to the Professor of Chemistry in 

 the College of Physicians and Surgeons, with the following result : 



COMPOSITION OF HUMAN PAROTID SALIVA. 



Water *. 983.300 



Organic matter precipitable by alcohol ..... 7.352 



Substance destructible by heat, but not precipitated by alcohol 

 or acids ........... 



Sulpho-cyanide of sodium. ....... 



Phosphate of liuie . 



Chloride of potassium ........ 



Chloride of sodium and carbonate of soda .... 



1000.00 



Mr. Perkins found, in accordance with our own observations, 

 that the fresh parotid saliva, when treated with perchloride of iron, 

 showed no evidences of sulpho-cyanogen ; but after the organic mat- 

 ters had been precipitated by alcohol, the filtered fluid was found 

 to contain an appreciable quantity of the sulpho-cyanide. 



The organic matter in the parotid saliva is in rather large quan- 

 tity as compared with the mineral ingredients. It is precipitable by 

 alcohol, by a boiling temperature, by ^nitric acid, and by sulphate 

 of soda in excess, but not by an acidulated solution of ferrocyanide 

 of potassium. It bears some resemblance, accordingly, to albumen, 

 but yet is not precisely identical with that substance. 



The parotid saliva also differs from the mixed saliva of the mouth 

 in containing some substance which masks the reaction of sulpho- 

 cyanogen. For if the parotid saliva and that from the mouth be 

 drawn from the same person within the same hour, the addition of 

 perchloride of iron will produce a distinct red color in the latter, while 

 no such change takes place in the former. And yet the parotid 



