444 STATE BOARD OF AGRICULTURE. 



Within 24 hours after adding the rennet extract to the sterile milk, 

 the milk in all flasks to which the imheated rennet filtrate had been 

 added showed digestion, the amount corresponding directly to the 

 amount of inoculum. At this time, a slight digestion was also noted 

 in the flasks containing 5 cc. and 1 cc. heated rennet extract and after 

 8 days the 25 cc. heated rennet extract had begun a decomposition of 

 the casein. The only explanation for the digestion of the milk in the 

 flasks containing the heated rennet solution is that during the boiling 

 over the free flame the coagulated albuminous substance of which there 

 was an abundant precipitate, enclosed the enzyme, protecting it from the 

 destructive action of the heiit. 



In this table it will be remarked that the varying quantities of germ- 

 free rennet extract added to the milk have no effect, either upon the 

 number of organisms per cc. at the end of 1 and of 8 days or upon the 

 amount of acid formed, i. e., the germ count per cc. of the heated rennet 

 filtrate at the end of 24 hours is 6i6,000,UU(), 500,000,000 and 478,000,000 

 while the corresponding acidities are 34°+, 37°+, and 36°+; of the 

 unheated rennet, 798,000,000, 852,000,000 and 682,000,000 with corres- 

 ponding acidities of 45°+, 44°+ and 44°. This same relation of 

 acidities is noted at the end of 8 days, the germ count at this time is 

 also comparable. This data is in direct contrast to that obtained from 

 varying the amounts of filtrate (see Tables XX and XXI) or of pepsin 

 solution. (See following table.) 



The heated rennet in all cases seems to have a markedly less stimula- 

 ting effect upon the lactic bacteria both in regard to multiplication and 

 acid production than the unheated rennet. In this respect the results 

 obtained are comparable with those from the experiments with the 

 filtrate and with the pepsin solution. (See Table XXVIII.) 



A glance at Table XXVIII will show the striking similarity between 

 the action of the germ-free pepsin solution and that of the filtrate of 

 LZ. (Compare Table XXVIII with Table XX.) 



In the foregoing experiments, it would seem that the rennet-like 

 enzyme produced by the yeast LZ is responsible in great part for the 

 stimulation of the reproductive activity and acid production of the 

 lactic bacteria and that the presence of the ])epsin-like enzyme retards 

 this stimulating effect as proportionate quantities of it are present. 

 Comparing Tables XXVII and XXVIII, a greater number of organisms 

 and larger quantities of acid are present in the rennet experiment than 

 in that of the pepsin. The results in Table XX are most similar to 

 those in Table XXVIII. 



Although the action of the filtrate upon the weak lactic bacterium 

 resembles that of the pepsin solution there is a difference in the ap- 

 pearance of the miriv in the two sets of flasks. The milk to which the 

 Stock lactic and unheated pepsin solution were added shows markedly 

 the characteristic peplic digestion while the milk to which the Stock 

 lactic and unheated filtrate were added apparently shows only the 

 shrinking of the curd and extrusion of the whey, it being difficult to 

 (IctcrTiiino tlio ])rosonce of a casein-digesting enzyme from the mere 

 physical appearance of the milk. 



