440 



STATE BOARD OF AGRICULTURE. 



determined by dividing the maximum number of organisms by the in- 

 itial number. It will be noted that the greatest diminution in numbers 

 as well as the highest bacterial count occurs in the lactic culture to 

 which was added the largest amount of inoculum of the jeast culture. 

 Similar results have been obtained previously with this same organism 

 and other lactic bacteria. (See Tables XVI, XVII, XVIII, XIX and 

 XX.) 



Expt. VI. 



Determination of the Length of Time that Weak Lactic Bacteria have 

 to Grow in Association with the Yeast LZ before their Vitality is 

 Restored. 



Along with Expt. V was carried on a similar experiment having the 

 following aims, first, to determine how long weak lactic bacteria have 

 to grow in association with the yeast LZ before they become typical, 

 and second, to determine whether any weak lactic organisms may so be 

 rejuvenated. 



The plan of this experiment is essentially that of the former. One 

 cubic centimeter of a milk culture of a weak lactic bacterium and 1 cc. 

 of a whey culture of LZ were added to 250 cc. of sterile milk, the flask 

 shaken well to distribute the organisms and plated immediately using 

 dilutions 1-200, 1-500 and 1-1,000. The plates were incubated at 

 37°C. for 2 days, then counted, giving colonies of the lactic bacterium 

 only. The milk flask containing the yeast plus the lactic organism and 

 also a check flask of the lactic organism were kept at room temperature, 

 21° — 25°C. As soon as the milk curded in either flask, both the mixed 

 culture and check were plated using dilutions 1-2,000,000, 1-5,000,000 

 and 1-10,000,000 and the acidity of each recorded. Forty-eight hours 

 after curding, plates were again made using the same dilutions and 

 the acidity recorded as before; these operations were continued about 

 every 8 days afterward. 



Each time plates were made a test culture was made, transferring 

 a loopful of the mixed culture to a litmus milk tube and placed at room 

 temperature; the time of curding of this culture was noted and when a 

 test culture curded in a noticeably shorter time it was plated and pure 

 cultures isolated to ascertain whether this characteristic was retained 

 in pure culture, successive transfers being made each day to determine 

 the constancy of the lactic loaction. I am indebted to Mr. L. ^f. llutch- 

 ins for the data in the following tables. 



A 5 weeks old culture of Lactone just curded was used in the experi- 

 ment tabulated in Table XXIII. 



TABLE XXin. 



