POLYPEPTIDES 79 



its use he was enabled to ascertain if the blood plasma underwent any 

 marked change after an animal had been bled ; beyond noting a decrease 

 in the rotation which soon disappeared no remarkable results were 

 noticed. An attempt was made to estimate the amount of blood in the 

 body by injecting dextrin into the blood stream and noting the change 

 in rotation after the dextrin had completely circulated. 



The detection of a proteoclastic enzyme in the blood of pregnant 

 animals can be carried out by placing the fresh serum, prepared free 

 from haemoglobin, in contact with pieces of placenta which have been 

 thoroughly washed with boiling acidulated water to remove peptones 

 and dialysing. Peptone diffuses out and its presence can be determined 

 by the biuret reaction, or better, by means of triketohydrindene hydrate. 



IV. Study of Enzyme Action. 



The optically active dipeptides form very suitable substrates for 

 investigating the rate of action of the proteoclastic enzymes under 

 various conditions as the changes in rotation are readily and quickly 

 observed. They have been used by Abderhalden in conjunction with 

 Michaelis, Gigon, Koelker, Brahm, Caemmeser and Pincussohn for 

 this purpose. Euler has also carried out experiments of this kind. 

 The observations conform with those of the previous observers using 

 other methods. Further details are given in the monograph by 

 Prof. W. M. Bayliss on the Nature of Enzyme Action. 



