54 GENERAL AND PHYSICO-CHEMICAL. 



sugar and of starch. ABDERHALDEN and his co-workers have shown 

 that the parenteral introduction of protein or peptone gives the blood 

 serum of the animal the power of splitting proteins, which power is 

 destroyed on heating to 60-65 C. 1 The introduction of very large quan- 

 tities of sugar or proteins per os (over feeding) has the same effect as 

 the parenteral introduction. ABDERHALDEN considers the active sub- 

 stances thus obtained as enzymes. The question is still undecided whether 

 the substances introduced bring about a formation of the enzymes or 

 whether they only transport the already formed enzymes to the blood. 



Heat Production. The question whether in the hydrolytic processes 

 with the aid of enzymes heat is given off or taken up has been attacked 

 in two different ways. GRAFE 2 could not find either any setting free or 

 taking up of heat in the digestion of protein in a RUBNER calorimeter. 

 On the other hand HARI 3 by determining the calorific values of albumin 

 before and after digestion came to about the same results. If we exclude 

 the work developed in the process then it follows that the energy supply 

 of the organism is not perceptibly changed by the hydrolytic cleavages 

 of the protein. The chief source of energy is to be sought in the oxida- 

 tion processes that follow the cleavages. 



Modes of Action of the Enzymes. The enzymes do not suffer any 

 appreciable change during the reaction they perform, and insignificant 

 amounts of the enzyme are able to decompose relatively enormous amounts 

 of the substrate. For example, 1 part of saccharase can invert 100,000 

 parts of cane-sugar (O'SuLLiVAN and THOMPSON) 4 and 1 part of rennin 

 can decompose more than 400,000 parts of casein (HAMMARSTEN) 5 . 

 For these reasons the enzymes have for a long time been considered as 

 catalytic substances. Nevertheless the enzyme reactions always take 

 place in heterogeneous media where on one hand the enzyme exists as 

 colloid and on the other the substrate in many cases is a colloid (starch, 

 proteins). As above mentioned, the enzymotic decompositions are 

 often complicated by their taking place over several intermediary steps 

 to the final product. As indicated by several conditions, the enzymes 

 also, before they act upon the substrate, combine therewith in some way 

 or another. The fact that the action of an enzyme is dependent upon the 

 stereometric construction (page 61) of the substrate speaks essentially 

 for this view. The substrate also protects certain enzymes against destruc- 



* Ibid., 61, 200; 62, 120, 243 (1909); 64, 100, 423, 426, 427; 66, 88; 69, 23 (1910); 

 71, 110, 367, 385 (1911). See also 77, 250 (1912). 

 2 Arch. f. Hygiene, 62, 216 (1907). 

 Pfluger's Arch., 115, 11 (1906); 121, 459 (1908). 

 4 Journ. chem. Soc., 57, 926 (1890). 

 6 See Maly's Jahresber, 7. 



