TRANSFERENCE OF FOOD MATERIALS 137 



the presence of adrenaline is necessary to the normal action 

 of the nerve endings.* 



Glycogen is stored in other parts than in the liver. The 

 muscles, owing to their large bulk, contain a total amount of 

 glycogen about the same as that in the liver (150 grams in 

 man). The placenta is another part where glycogen is stored 

 as a reserve for the growing embryo. 



Absorption of Proteins. Some years ago the final products 

 of digestion of proteins were believed to be peptones. As no 

 peptone could be found in the blood during digestion of proteins 

 it was assumed that like the fats the proteins were 

 resynthesised in the cells of the intestinal mucous membrane. 

 Now that it is known that most of the protein is decomposed 

 into amino acids these substances have been sought in the 

 blood. The bulk of the evidence is in favour of the absorption 

 of amino acids. 



The method of Abel, which consists in passing blood through 

 a series of collodium tubes so that a great surface is exposed 

 for diffusion into a solution outside the tubes, shows that 

 amino acids are present in blood and the same method ought 

 to settle whether the bulk of digested protein finds its way 

 into the blood as amino acids. | 



The amino acids are taken from the blood by the individual 

 cells according to their needs and the excess of any amino 

 acids are deamidised and removed from the circulating medium . 



Digestion of Cellulose. Bacterial decomposition in the 

 intestine leads to the formation of various substances not 

 present in the food. These processes are more conveniently 

 described in relation to other bacterial processes, but the 

 bacterial decomposition of cellulose is important in relation to 

 digestion. No enzyme capable of hydrolysing cellulose has 

 been found in mammals but in the large intestine of the 

 horse and the stomach of ruminants cellulose is acted on by 

 bacteria so that soluble substances (organic acids) are formed 

 which can be absorbed and used in metabolism. J 



Some invertebrates possess the power of digesting cellulose, 

 for instance an enzyme can be obtained from the liver of the 

 snail which dissolves cellulose. 



* J. J. R. McLeod and R. G. Pearce, Amer. Journ. Physiol., 1911, 

 vol. 29, p. 419. 



f J. J. Abel, L. G. Rowntree and B. B. Turner, Journ. Pharm. 

 and Exper. Therap., 1914, vol. 5, p. 275. 



J H. Tappeiner, Zeit. f. Biol., 1884, vol. 20, p. 52. 



W. Biedermann and P. Moritz, Arch. f. d. ges. Physiol., 1898, 

 vol. 73, p. 219. 



