60 LECTURE IV. 



special ferment, called glucase (or maltase). 1 This last action plays a 

 subordinate part in the total action of the saliva. The transformation 

 of the starch past the dextrin stage into maltose does not take place so 

 simply as might seem possible. A great many intermediate products have 

 been described. At present there is no reason for going into the details here, 

 partly because we are not sure whether some of these products are single 

 substances, or mixtures of several constituents. 



The human saliva, or rather the amylolytic ferment contained in it, 

 does not attack raw starch to any extent. In almost every case the 

 starch has already undergone a process of change which greatly facil- 

 itates the action of the diastase upon it. In most cases the starch has 

 been cooked, which swells the grains. The fact that this is favorable to 

 the action of the diastase can be easily shown by the following experiment : 

 In one test-tube a few grains of ordinary starch are mixed with saliva, 

 while in another the same saliva is allowed to act for an equal length of 

 time upon starch paste. If at the end of a certain length of time iodine is 

 added to test for unchanged starch, a much stronger coloration will be 

 obtained in the first tube than in the second. If, on the other hand, we 

 test for the sugar 2 formed, we shall this time obtain a better test in the 

 other test-tube. 



Leaving the mouth, the starch, together with some of its transformation 

 products, all intimately mixed with the saliva, reaches the stomach. 

 For a long time it was believed that the action of the diastase quickly 

 stopped here on account of the acid reaction of the contents of the stomach. 

 Free hydrochloric acid is especially unfavorable to the action of diastase; 

 as little as 0.03 per cent prevents it from changing starch into sugar. 

 Recent experiments 3 have shown, however, that the food reaching the 

 stomach is not immediately mixed with the gastric juice as was formerly 

 assumed, but on the contrary lies out of contact with this for some time. 

 In the stomach itself there has not been found any agent capable of con- 

 verting carbohydrates into sugar, 4 but, on the other hand, a not incon- 

 siderable absorption of the simple sugar formed is known to take place 

 here. 



The main digestion of carbohydrates is effected, however, in the intes- 

 tine by the action of a diastase from the pancreas. By means of it the 

 starch which for the greater part is still unchanged, or at least only very 



1 M. C. Tebb: J. Physiol. 15, 421 (1894). Hamburger: Pfliiger's Archiv. 60, 543 

 (1895). 



2 Naturally, the saliva, starch, and starch paste should be examined for sugar at the 

 start. 



3 P. Griitzner: Pfliiger's Arch. 106, 463 (1905). 



4 According to H. Friedenthal, the stomach juices of a dog contain a ferment which 

 acts strongly in acid solutions. Archiv. (Anat. und) Physiol. 1899, Suppl. 383. 



