DIGESTION. 171 



Sulphocyanides, which, although not constant, occur in the 

 saliva of man and certain animals, may be easily detected by first 

 acidifying the saliva with hydrochloric acid and treating with a very 

 dilute solution of ferric chloride. To make the test more conclusive 

 it is best, as control, to take an equal quantity of acidified water 

 and then add ferric chloride. Another, simpler method, proposed 

 by GSCHEIDLEN, consists in putting in a drop or two of the saliva 

 on filter-paper which has previously been dipped in an amber- 

 colored solution of ferric chloride containing hydrochloric acid, and 

 then dried. Each drop of saliva containing sulphocyanide will 

 give a reddish spot. If the quantity of sulphocyanide is so small 

 that it cannot be detected directly, concentrate the saliva after the 

 addition of a little alkali, acidify strongly with hydrochloric acid, 

 and shake repeatedly with ether, evaporating the latter after the 

 addition .of water containing alkali over a gentle heat; then test the 

 remaining liquid. 



Ptyalin, or salivary diastase, is the amylolytic ferment of the 

 saliva. This ferment is found in human saliva, but not in that of 

 animals. It occurs not only in adults, but also in new-born 

 infants. ZWEIFEL claims that the ptyalin in new-born infants 

 occurs only in the parotid gland, but not in the submaxillary. In 

 the latter it appears only two months after birth. 



Ptyalin has not been isolated in a pure form up to the present 

 time. It was obtained purest by precipitation with calcium phos- 

 phate (COHNHEIM). For the study or the demonstration of the 

 action of ptyalin we may use a watery or glycerin extract of the 

 salivary glands, or, more simply, the saliva itself. 



Ptyalin, like other enzymes, is characterized by its action. This 

 consists in converting starch into dextrin and sugar. According to 

 the common acceptation, soluble starch is first formed by this action 

 and then erythro-dextrin, which is further changed so that we 

 obtain at the end achroo-dextrin and maltose with a small admix- 

 ture of glucose. Like starch, glycogen is also split by ptyalin into 

 dextrin and sugar (apparently maltose) upon the addition of water. 

 Ptyalin is not identical with malt diastase; while the first acts with 

 greatest energy at about -f 40 0., diastase acts best at + 50 to 

 55 0. (CHITTENDEN and MARTIN). 



Ptyalin acts in faintly alkaline, in neutral, and in extremely weak 

 acid solutions. It seems to act most energetically in neutral or, in 

 a few cases, in very faint acid reaction (CHITTENDEN and SCHMIDT). 



