PAROTID SALIVA. 15 



removed by carbonic acid, or some other means. The alkaline 

 solution of this substance yields, on the addition of a little acetic 

 or nitric acid, a flocculent precipitate, which dissolves freely in an 

 excess of acetic acid; when boiled with hydrochlorate of am- 

 monia, or with sulphate of magnesia, the alkaline solution of 

 ptyalin becomes strongly turbid. The alkaline (but not the 

 neutralised) solution of this substance is precipitated by tannic 

 acid, corrosive sublimate, and basic acetate of lead, but not by 

 alum or sulphate of copper. The acetic acid solution becomes 

 strongly turbid on the addition of ferrocyanide of potassium ; 

 when boiled with nitric acid, this substance forms a yellow solution. 

 In these respects, it is very similar to albuminate of soda, and to 

 casein, but it must by no means be confounded with them. I have 

 principally studied the properties of this substance in cases in 

 which it had been obtained from the parotid saliva of the horse, 

 and I have arrived at the conclusion, that the differences observed 

 by Berzelius, Gmelin, and others, in reference to ptyalin, may 

 be easily explained. In no other animal fluids could I recognise 

 a substance perfectly identical with this ptyalin. 



It is singular that Magendie, in his investigations regarding the 

 parotid saliva, has overlooked the circumstance that it abounds in 

 lime (and assumes only the presence of bicarbonate of potash) ; 

 while Jacubowitsch* constantly found carbonate of lime in the 

 parotid saliva of dogs. It is possible that differences of food may 

 exert the same influence on the saliva as they do on the urine of 

 horses ; for, as we shall subsequently show, the urine of these 

 animals sometimes abounds in carbonate of potash, and sometimes 

 in carbonate of lime ; but whenever I analysed the saliva of the 

 horse, I always found it very rich in lime. 



(b) An extractive matter soluble in alcohol and in water, which 

 is precipitable by tannic acid, but not by alum. 



(c) Sulphocyanide of potassium,) whose presence has been de- 

 tected by Mitscherlich, Jacubowitsch, and Gmelin, in the parotid 

 saliva of man, the dog, the horse, and the sheep. 



I have not observed any reddening on the addition of per- 

 chloride of iron to the parotid secretion of the horse. 



(d) The potash-salt of a not very volatile acid belonging to the 

 butyric acid group (caproic acid ?) ; it crystallises in a beautiful 

 efflorescent form, which, under the microscope, resembles the 

 tufts of rnargaric acid. 



(e) A little epithelium) and some scattered mucus-corpuscles. 



* Op. cit. p. 20-22. 



