50 GENERAL AND PHYSICO-CHEMICAL. 



aqueous solutions, and even at ordinary -temperature the enzymes are 

 gradually decomposed. In general the enzymes lose their activity by 

 heating for a short time to 70 C. MADSEN and WALBUM have followed 

 this process at different temperatures and found that the decomposition 

 of trypsin, pepsin and rennin at given temperatures proceeds mono- 

 molecularly, i.e., that the velocity of reaction at every moment is pro- 

 portional to the concentration of the enzyme (page 34) . l The readiness 

 with which an enzyme is decomposed is nevertheless to a great extent 

 dependent upon the presence of other bodies (page 54). 



Certain enzymes are also sensitive to light. According to SCHMIDT- 

 NIELSEN 2 rennin is injured by light and in particular, by the ultra-violet 

 rays. The experiments of JODLBAUER and TAPPEINER S with invertin 

 have led to the same results; the visible rays can also in some cases 

 (peroxidase, hsemase) in the presence of oxygen or certain fluorescent 

 substances exert an injurious action. 4 



According to SCHMIDT-NIELSEN 5 the weakening in the rennin under 

 the influence of light proceeds like a monomolecular reaction. 



Experiments on the cataphoresis of enzymes have been made by 

 BIERRY, HENRY and SCHAEFFER 6 as well as by MICHAELIS. . These 

 investigators found that saccharase migrates to the anode. MICHAELIS 7 

 found that the migration direction of other enzymes was dependent upon 

 the reaction, namely in faintly acid reaction they moved to the cathode 

 and in faintly alkaline reaction to the anode. Recently PEKELHARING 

 and W. E. RINGER 8 have observed that the migration direction of pig 

 pepsin was very materially influenced by the addition of small amounts 

 of proteoses. From what was previously stated (page 20) the saccharase 

 must therefore have a negative charge. As MiCHAELis, 9 has on the other 

 hand, found that the saccharase can be adsorbed by the positively 

 charged aluminium hydrate and not by the negatively charged kaolin, 

 he concludes that the formation of adsorption compounds, at least in 

 certain cases, depends upon an opposed electric charge of the two com- 

 ponents. 



1 Arrhenius, Immunochemie, Leipzig, 1907, 58. 



* Hofmeister's Beitrage, 5,355(1904); 8,481(1906); Zeitschr. f. physiol. Chem., 58, 

 233 (1908). 



8 Arch. f. klin. Med., 87, 373 (1906). 



4 Bioch. Zeitschr., 8, 61 and 84 (1908). See also Agulhon, Compt. rend., 163, 979 

 (1911). 



6 Zeitschr. f. physiol. Chem., 58, 232 (1908). 



6 Compt. rend. soc. biol., 63, 226 (1907). 



7 Bioch. Zeitschr., 16, 81, 486; 17, 231 (1909). 



8 Zeitschr. f. physiol. Chem., 75, 282 (1911). 



9 Bioch. Zeitchr., 10, 299 (1908). 



