130 LECTURES ON IMMUNITY 



seems to occur at about 37 C. In the interval, 30-90 

 min., the optimum seems to lie at about 33 C., and in the 

 interval 90-180 min. at about 29 C. The position of the 

 optimum evidently depends on how rapidly the experi- 

 mental manipulations are done. If it were possible to 

 examine K immediately after mixing the reagents, the 

 optimum would probably be found to lie at a much higher 

 temperature; or there would perhaps be no optimum at 

 all. 



It is worthy of mention that the dry cytoplasma sus- 

 pended in pure oil resists a temperature of 100 C. for 

 twenty hours ; at 120 C. its activity decreases one-third in 

 a quarter of an hour. 



Quite recently A. E. Taylor 1 has carried out an investi- 

 gation on the action of the lipase from the castor bean on 

 the triglycerid of acetic acid, commonly termed triacetin. 

 This compound is rather soluble in water, so that homoge- 

 neous solutions were prepared containing 0.5, I, or 2 per 

 cent (up to 3 per cent) of triacetin together with i g. of the 

 powder of castor beans, from which the fat had been 

 extracted, in looc.c. of water. The following values 

 were obtained, indicating a monomolecular process. The 



I A. 

 velocity-constant is K =- log io 4 - 



t ./JL ~ X 



The agreement between the three values of K indicates 

 that the decomposed quantity is very closely proportional 

 to the quantity of the substrate. The regularity of this 

 process is evidently higher than that of any other ferment- 

 ative action hitherto studied. The velocity of reaction in- 

 creased in the proportion of i to 2.6 if the temperature 



1 A. E. Taylor: Journ. Biol. Chemistry, 2. 87 (1906). 



