24 



BULLETIN 139, U. S. DEPARTMENT OP AGRICULTURE. 



show the remarkable difference in growth of organisms of the colon- 

 aerogenes group in milk held at 50° F. (10° C), compared with 70° F. 

 (21° C). While there is some indication of slight growth in a few of 

 the samples held at 50° F. (10° C), there was the rapid multiplication 

 of the organisms in milk held at 70° F. (21° C), the average colon 

 count in 20 samples held for 24 hours at this temperature being 

 7,385,500 per cubic centimeter. 



Table 13. — Growth of organisvis of colon-aerogenes group at 50° F. (10° C.) and 70° F. 



(21.1° C). 



Sample 

 No. 



Total count. 



Colon count. 1 







Held for 



Held for 24 



Fresh. 



Fresh. 



24 hours 

 at 50° F. 



hours at 

 70° F. 









(10° C). 



(21.1° C). 



1 



225,000 







100 



180, 000 



2 



1, 140, 000 



28,400 



83,000 



55, 500, 000 



3 



270, 000 







200 



2, 600, 000 



4 



680,000 











2,350,000 



5 



1,080,000 











3, 400, 000 



6 



490, 000 







800 



5, 100, 000 



7 



850, 000 



900 



1,300 



8, 300, 000 



8 



840, 000 







200 



2,700,000 



9 



1, 450, 000 







600 



2,520,000 



10 



2,400,000 











12, 800, 000 



11 



1, 950, 000 











22, 000, 000 



12 



260, 000 











1,250,000 



13 



610, 000 



2,000 



600 



15,300,000 



14 



340, 000 











830,000 



15 



630, 000 











1,170,000 



16 



179, 000 











1, 180, 000 



17 



366, 000 











6,400,000 



18 



304,000 











120, 000 



19 



460,000 











1,810,000 



20 



620,000 







400 



2, 200, 000 



1 indicates none in T J 5 of a cubic centimeter. 



Further studies on the growth of organisms of the colon-aerogenes 

 group at different temperatures are shown in Table 14. Three dif- 

 ferent sets of conditions were used so as to determine the subsequent 

 growth in three distinct grades of fresh milk. Special attention is 

 called to the colon counts after the milk had been held for 6 hours at 

 86° F. (30° C.k Among the 22 samples of milk produced in the 

 dirty barn and handled in sterilized utensils there was practically 

 no increase in the colon count after 6 hours at 86° F. (30° C), but 

 after 24 hours at the same temperature the colon count had reached 

 the high figure of 63,279,545 per cubic centimeter. Twenty-six 

 samples produced in the dirty barn and handled in unsterilized 

 utensils showed after 6 hours a distinct increase in the colon count 

 in most of the samples, and after 24 hours the colon count averaged 

 about 24,000,000 per cubic centimeter. 



Similar increases occurred among the 20 samples produced in a 

 dirty barn and handled in unsterilized utensils which had not been 

 washed until 8 hours after milking. The average colon count of the 

 fresh milk was 595 per cubic centimeter. After 6 hours, at 86° F. 

 (30° C.) the average count had increased to 37,525, while after 24 



