FUNCTIONS OF THE SALIVA. 31 



rudimentary organs, while their submaxillary glands for the elabo- 

 ration of mucus are for the most part very well developed. 



The chemical function of the saliva is a subject on which 

 different observers have held very different views. Leuchs was 

 the first who was led by experimental inquiry to the discovery 

 that starch is gradually converted into sugar by the action 

 of the saliva. Subsequent inquirers who have repeated the experi- 

 ments in some instances confirm, and in others deny, the accuracy 

 of his views. Wright, who bases his view on a large number of 

 experiments, speaks very decisively in favour of the chemical 

 action of saliva on amylaceous food; and indeed, Mialhe* 

 believed that he had actually discovered the substance in which 

 this metamorphic power solely or for the most part resides, and 

 gave it the name of salivary diastase. Several observers, having 

 failed in attempting to confirm the views of Wright and Mialhe, 

 have directed their attention to the individual secretions of the 

 different glands. Magendie was the first who discovered that 

 neither the parotid nor the submaxillary secretion exerts any 

 action on starch, but that the common or mixed saliva of the horse 

 converts both crude and boiled starch into sugar at the tempera- 

 ture of the animal body ; Bernard attributed this unquestionable 

 property of the mixed saliva (whether obtained from man, the dog, 

 or the horse), solely to the buccal secretion, while Jacubowitsch 

 has adduced convincing evidence that this secretion alone does not 

 possess the above property which exists only in the mixture 

 (whether artificial or natural) of the secretions of the buccal 

 mucous membrane and the salivary glands. It can therefore no 

 longer be doubted that the saliva, in the normal condition in which 

 it is mixed with the food, possesses the property of converting 

 starch into sugar. We by no means, however, agree with Ross t in 

 regarding the buccal cavity as the stomach for vegetable food. 

 Even under the most favourable circumstances we cannot detect a 

 trace of sugar in a mixture of saliva and boiled starch, in less than 

 from 5 to 10 minutes ; and hence, if the conversion of amylaceous 

 matter into sugar be the physiological function of the saliva, its 

 action must not be confined to the short time in which the food 

 remains in the mouth, but must also be continued in the stomach 

 and intestines. Now we may readily convince ourselves that this 

 is really the case, by observing what occurs in an animal in whom 

 a gastric fistula has been established ; for while pure gastric juice 



* Compt. rend. T. 20, pp. 247, 367, 954, et 1485. 

 t The Lancet, January 13, 1844. 



