62 LECTURE IV. 



from which the organism is able to build up its own individual 

 carbohydrates. 



Before we attempt to follow the simple sugars on their way to the 

 organs, or, in other words, to study the course taken in their absorption, we 

 must consider what takes place in the case of a few compound carbo- 

 hydrates which form an important part of our food. We refer to milk- 

 sugar which occurs in milk, and the numerous carbohydrates other than 

 starch that are obtained in vegetable nutriment, cellulose especially. 

 Milk-sugar is unquestionably decomposed into its components while in 

 the bowels in the case of animals accustomed to milk nourishment, espe- 

 cially during the age of suckling. 1 On the other hand, in many animals 

 there seems to be no ferment present in the whole of the alimentary canal 

 which is capable of splitting up milk-sugar. What happens to milk-sugar 

 in such cases is not clear to us at present; probably it is further decom- 

 posed in the wall of the canal. The question as to the utilization of car- 

 bohydrate introduced into the organism in the form of cellulose is a very 

 important one. Cellulose plays no part at all in the nourishment of the 

 carnivora, and it is also unessential in the case of the omnivora, whereas 

 in the case of the herbivora a not inconsiderable part of the carbohydrates 

 contained in their nourishment is in the form of cellulose. Now, this 

 compound is not acted upon by the saliva, nor by the juices of the stomach, 

 pancreas, or intestine, provided we leave out of consideration the action 

 of bacteria which are ever-present. It is here that the activity of certain 

 micro-organisms present in the intestines comes into play, and this forms 

 to some extent an example of symbiosis. The fact that cellulose is actually 

 subject to a transformation in the bowels is proved by our being unable 

 to find in the fseces the whole amount of cellulose which has been introduced 

 into the system. 2 Outside of the organism, it has been found possible to 

 dissolve as much as seventy per cent of cellulose by means of the intestinal 

 juices from a horse; these are rich in bacteria. 3 Sugar is not formed by 

 this process, but a considerable amount of gas is evolved. The mixture 

 produced by the decomposition has an acid reaction. These products 

 have been studied by Tappeiner. 4 He found that by the action of meat 



1 Cf. Rohmann and Nagano: Pfliiger's Arch. 95 60 (1903); Ernst Weinland: Z. 

 Biol. 38, 16, and 606 (1899); 40 (1900). 



2 The food-value of cellulose has not been determined definitely even as regards the 

 herbivora. Cf. the following articles: W. Henneberg and F. Stohmann: " Beitriige zu 

 einer rationellen Fiitterung der Wiederkauer," Braunschweig, 1860 and 1864. Z. Biol. 

 21, 613 (1885). v. Knieriem: ibid. 21, 67 (1885). Weiske, Schulze, and Flechsig: ibid. 

 22, 373 (1886). E. Wolff: Landwirtsch. Jahrbucher, 49, Suppl. Ill (1887). N. Zuntz: 

 Pfliiger's Arch. 49, 477 (1891). 



3 Viktor Hofmeister: Arch, wissensch. und prakt. Heilkunde, 11, 1 and 2 (1885). 



4 Z. Biol. 20, 52 (1884) ; 24, 105 (1888) ; and Hoppe-Seyler: Z. physiol. Chem. 10, 401 

 (1886). 



