2IO Report of the Chemical Department of the 



destroyed by heat and all organisms were rendered inactive by 

 chloroform. 



(5) In comparison zvith commercial pepsin on paracasein dilactatc. 

 — In these experiments, rennet-enzyme and commercial pepsin, 

 sterilized by formaldehyde, were allowed to act upon sterile para- 

 casein dilactate. 



The results of these experiments appear to us to justify the 

 following statements: 



(i) In the case of every experiment made, whether with cheese 

 or milk, there was little or no proteolytic action of either rennet- 

 enzyme or commercial pepsin in the absence of acid; while there 

 was marked action, though in varying degrees, in the presence 

 of acid. 



(2) In the absence of acid in cheese, no paracasein lactate is 

 formed and little or no proteolysis occurs; in the presence of acid 

 in cheese, or more strictly in the milk and curd, paracasein mono- 

 lactate is formed and proteolysis takes place, with the rennet- 

 ferment as the active agent. The ability of rennet-enzyme to 

 convert paracasein into soluble nitrogen compounds appears to 

 depend upon the presence of paracasin lactate. In cheese-mak- 

 ing, therefore, the primary function of acid appears to be the 

 formation of a chemical compound with paracasein, commonly 

 paracasein monolactate but, in excess of acid, paracasein dilactate. 

 The conversion of parcasein monolactate by rennet-enzyme into 

 soluble nitrogen compounds is strongly suggested by the fact 

 that, when the soluble nitrogen compounds increase, the para- 

 casein monolactate decreases. 



(3) In comparing rennet-enzyme and commercial pepsin in the 

 case of cheese, milk and paracasein dilactate, the experiments that 

 were strictly parallel have shown about the same extent of 

 proteolytic action. 



(4) In the case of both rennet-enzyme and commercial pepsin, 

 the chemical work performed by the ferments is confined mainly 

 to the formation of paranuclein, caseoses and peptones, while 

 only small amounts of amides are formed, and no ammonia. 



(5) Rennet-enzyme is a peptic ferment, as shown by the follow- 

 ing characteristics : (o) neither rennet-enzyme nor pepsin causes 

 much, if any, proteolytic change, except with the help of acid; 

 {h) the quantitative results of proteolysis furnished by rennet- 



