166 THE PROCESSES OF DIGESTION AND RESORPTION. 



sively decomposed by hydrolysis into erythrodextrin, aehroSdextrin, 

 isomaltose, and finally into maltose, as shown by the equations : 



(1) (CulLoOio)* + 3H 2 = 3[(C 12 H 20 10 U.C 1? H 22 O n ] 



Amidulin. Erythrodextrin. 



(2) 3[(C 12 H 20 10 ) 17 .C 12 H 22 O n ] + 6H 2 = 9[(^ 2 H 20 q io ) 5 .C J2 H 22 O n ] 



Erythrodextrin. Achroodextrin. 



(3) 9[(C 12 H. 20 10 ) 5 .C 12 H 22 11 ] + 45H 2 - 54C 12 H 22 O n = 54C ]2 H 22 O U 



Achroodextrm. Isomaltose. Maltose. 



Glycogen is similarly decomposed, and, like starch, gives rise to 

 the formation of isomaltose and maltose. The celluloses, on the 

 other hand, are not affected by ptyalin, nor, indeed, by any of the 

 digestive fluids. As we shall see, however, they undergo a certain 

 kind of fermentation under the influence of various bacteria, and 

 as a result we find that in herbivorous animals, at least, only a frac- 

 tion of the ingested cellulose reappears in the feces. Thus far a 



transformation into maltose or glucose has not been observed in the 

 

 intestinal tract. 



It is stated that through the activity of the bacteria of the intesti- 

 nal canal, viz., their ferments, a certain amount of starch is trans- 

 formed into maltose, and that inversion of disaccharides to mono- 

 saccharides is likewise brought about in this manner. To what 

 extent this bacterial action can be regarded as representing an actual 

 digestion is, however, an open question. The presence of bacteria 

 in the intestinal canal is certainly not imperative, as has been con- 

 clusively established by Nuttall and Thierfelder; and we know, 

 moreover, that bacterial action extends far beyond the action of 

 digestive ferments, and that the further changes that can thus be 

 effected do not serve a useful purpose. The normal inversion of 

 the disaccharides is unquestionably brought about by the invertin, 

 maltase, and lactase, which, as has been indicated, are partly fur- 

 nished by the pancreas, but principally by the enteric juice. This 

 inversion is likewise of the nature of a hydrolytic process, and may 

 be represented by the general equation : 



C 12 H 22 O y + H 2 : 2C 6 H 12 6 



Disaccnaride. Monosacchanue. 



To judge from certain experiments which have been performed 

 on animals, it appears, however, that amylolysis at least can also 

 take place in the absence of the principal gland by which the 

 ptyalin is formed, viz., the pancreas. For we find that following 

 the extirpation of this organ or ligation of the pancreatic duct dogs 

 are still capable of utilizing as much as from 47 to 71 per cent, of 

 the starch ingested. As the dog's saliva contains no ptyalin, the 

 amylolysis cannot be referable to a converting activity of the salivary 

 glands. Whether in such cases the small amount of the ferment 

 which is also furnished by the enteric juice is sufficient to transform 

 the ingested starch into maltose is questionable, and there is some 

 reason for supposing that the epithelial cells of the small intestine 



