STARCH. 275 



fully discussed these points in the second volume., when treating 

 of the functions of the saliva (pp. 30-40) and of the pancreatic 

 juice (p. 120), that very few additional remarks are necessary. 



If we briefly review the history of starch within the animal 

 organism, commencing with its introduction into the mouth, we 

 find that in this cavity it is more or less impregnated with saliva 

 according to the intensity of the movements of mastication, its 

 own dryness, and other circumstances. Powerfully as normal 

 saliva occasions the transformation of boiled starch into sugar, its 

 influence on the raw starch during the short time that each 

 morsel remains in the mouth must be extremely slight. In the 

 ruminating animals, on the other hand, where the food is for a 

 long time retained in the paunch, and where from the continuous 

 flow of saliva it is exposed to the prolonged action of this 

 secretion, a great part of th'e starch contained in the food must 

 certainly be metamorphosed ; and the same must be the case in 

 the crop of the bird. In all other animals the greater part of the 

 starch passes unchanged into the stomach, where the further 

 action of the saliva upon it is to a certain degree suspended by the 

 gastric juice, when secreted in sufficient quantity. After a due 

 sojourn in the stomach this substance passes into the duodenum, 

 where it is brought in contact with the powerfully acting pan- 

 creatic juice, and the commencement of its metamorphosis ensues. 

 Towards the ileum the pancreatic juice disappears, and in its place 

 we find the intestinal juice, which acts somewhat less energetically 

 in effecting the metamorphosis of the starch. The conversion 

 of the starch into sugar gradually follows; the starch -granules 

 become softened on their surface, and, as they dissolve, become 

 converted into dextrin and sugar. Individual lamellae become 

 separated from the granules, and undergo more or less disintegra- 

 tion, isolated shreds being often perceptible by the microscope after 

 the application of iodine. The farther the starch passes onwards 

 from the jejunum into the ileum, so much the smaller do the 

 granules appear in consequence of the above-mentioned solution 

 of their surface. The enormous development of the caecum in 

 herbivorous animals seems to indicate that the amylaceous matters 

 are here again exposed to the action of a ferment which exerts 

 some change upon them : but the experiments which have been 

 hitherto made afford no evidence either in favour of or against the 

 view that the glandular secretions which are there poured forth 

 actually yield such a ferment. We know that the first product 

 of the decomposition of starch, dextrin, is so rapidly converted 



T 2 



