ITS DIGESTIVE POWER. 35 



believed that I had obtained a somewhat similar result, I have 

 since convinced myself that the metamorphosing force is neither 

 concentrated in the admixture of substances indicated by Mialhe 

 or by myself, nor yet in any other part of the extractive matters 

 of the saliva. In the mean time, it would be unscientific to 

 neglect all inquiry regarding this peculiarity of the saliva, or 

 rather of one of its constituents, and to rest satisfied with the 

 fiction that all exciters of fermentation are substances undergoing 

 changes, and that such substances are incapable of being submitted 

 to chemical exhibition and investigation. All fictions that close 

 the door on inquiry are to be rejected, unless they admit of a 

 logical justification. If Schwann, Wasmann, and others, had 

 remained satisfied with the conviction that the cause of the 

 digestive power of the gastric juice did not admit of being investi- 

 gated, we should not have advanced very far in the knowledge of 

 the process of digestion. We can hardly condemn an inquiry into 

 the hypothetical diastase of the saliva as absurd ; for the saliva 

 does not lose this property either by the action of heat or alcohol, 

 and pepsin similarly retains its power even after having pre- 

 viously been combined with salts of lead. This much, however, is 

 certain, that the ptyalin obtained by Berzelius, Gmelin, and 

 Wright, was found in all cases to be deficient in the power of 

 converting starch into sugar. 



After it had been demonstrated, as already observed, first by 

 Magendie, and subsequently by Bernard, that the secretions of 

 some of the salivary glands did not exert any metamorphic action 

 on starch, Jacubowitsch, under the direction of Bidder and 

 Schmidt, prosecuted some admirable experiments on this subject, 

 which we do not think it will be irrelevant to notice at some 

 length in the present place. He convinced himself, by hindering 

 the flow of the secretions of the parotid and submaxillary glands 

 from entering into the mouth of a dog, that the mere secretion 

 of the mucous membrane of the mouth (contrary to Bernard's 

 assertion) was unable to convert starch into sugar. But when he 

 tied the ducts of only a single pair of glands (excluding only the 

 secretion from the parotid or that from the submaxillary glands), and 

 suffered the dog to recover after the operation, and then, according 

 to Bernard's method, as already described, digested starch with 

 the saliva exuding from the open and depressed mouth of the dog, 

 some of the starch was converted into sugar in the course of five 

 minutes. The starch was also quickly metamorphosed when 

 brought in contact with an artificial admixture of the above- 



D 2 



