Physical Chiomi.stkv and Victerinarv Sciknck. 189 



surticieiit to make it act as an tnt-tjmp^ because not eveiy colloid has a 

 catalytic effect. 



Enzymes are found nearly everywliere in the or<^anism, in the 

 blood and within the cells (Jakoby). Their number is very jj;reat, 

 their actual (luantity comparatively small and their functions multiple, 

 namely, dissolutions, coagulations, hydrolytic processes, syntheses, de- 

 compositions, condensations, and polymerisations, oxydations and re- 

 ductions. In the organism probabl}' every chemical process and several 

 merely physical reactions need enzymes. As a rule there is one specific 

 enzyn\e for each reaction, and the localisation is guaranteed bv the 

 colloidal state of the enzymes and the structure of the cell membi-ane 

 and the protoplasma (compare later). 



We might divide the enzymes of the organism into two groups 

 (ct>mpare Euler). To the first group belong those which are able to act 

 quite alone on the respective substrate, whilst those of the second 

 group need another substance in company with which they show the 

 typical effect. The latter substances are called acfAvufors, kinases or 

 co-enzymes. This is a parallel phenomenon to the combined action of 

 the immune substances sensibilisator and alexine on a cell or to the 

 activation of one colloid by another (saponine -|- taurocholic Na, Frei, 

 snake venom -\- lecithine, Kyes), and it was possible to substitute the 

 activator of pancreatic juice by the colloidal toluidine blue (Lai-guier 

 des Bancels). 



Ions have either an accelerative or proti-acting influence (com- 

 pare immune bodies). There are some substances which act tlirectly 

 as poisons on inorganic and organic enzymes (iodine, phosphorus, 

 hydrocyanic acid). The paralysing eflfect is still remarkable in enor- 

 mous dilutions ; for instance, a proti'action of the catalysis of colloidal 

 platina is cau.sed by iodine even in a dilution of O'OOOOOOl gramme 

 molecule per litre (Bredig). 



Injection of enzymes into an animal gives rise to specific anti- 

 bodies, anti-enzymes, which paralyse the functions of the enz^mies or 

 even accelerate a reaction adverse to the reaction of the original 

 enzj^me (Beitzke and Neuberg). 



The enzyme reactions take place in heterogeneous systems. There 

 is no doubt that the enormous total surface stipulated by the colloidal 

 nature of the enzymes is dominant in their functions. Considerable 

 absorptions on this surface cause an increase of concentration of the 

 substrate on them, and thus facilitate the reaction. Evidently the con- 

 ditions for diffusion in the medium interfere, and the speed of diffusion 

 to the surfaces and away from them influence also the velocity of the 

 total reaction. 



(e) The Cells. 



Until now we have dealt with liquids without visible structure 

 (although it is quite possible that the colloids mentioned have a certain 

 internal structure). It remains to explain the chief points of the 

 physical-chemical conception of morphological constituents of the 



