SIGNIFICANCE OF COLON COUNT IN MILK. 
Table 3. — Nature of colon-aerogenes contamination from the atmosphere (20 liters of air 
drawn through 20 cubic centimeters of sterile milk). 
Examination of milk. 
Location of air. 
Fresh. 
After 24 hours at 70° F. (21.1° C). 
Colon 
count. 1 
B. coli. 
B. aero- 
genes. 
Colon 
count. 1 
B. coli. 
B. aero- 
genes. 

















2,100 


200 

Per cent. 



Per cent. 



36,000 
140,000 
18,000,000 


5,000 
4,000,000 
1,700,000 
27, 000 

230. 000, 000 
205,000,000 
680,000 
230, 000 
12, 800, 000 
12, 700, 000 

14,000,000 

6,700,000 
7,500,000 
60,000 
Per cent. 
91 
93 
98 
Per cent. 
9 
Do 
7 
2 
Do 

92 
100 

100 


8 

100 
Do 
Do 



83 

8 
100 
Do 
100 
Do 
100 
17 
Do 
100 
92 
Do 
Do 

100 

100 
Do 



100 
Do 

100 
100 
Do 
100 
1 means none in 1/100 of a cubic centimeter of milk. 
It is of further interest to note that after enrichment in sterile milk 
the majority of samples contained organisms mostly of the B. aero- 
genes type, although in a few there was a large proportion of the 
B. coli type. It is not surprising that organisms of the B. coli type 
can be found in barn air, for they are present in large numbers in 
fresh cow feces, and probably actually multiply as the feces become 
dry. Evidence of this is furnished in Table 4, in which a composite 
sample of feces from 4 cows was examined when fresh, and again 
after 2, 10, and 14 days. The colon count is given per gram on both 
the dry and the wet basis. The calculations of the count on a dry basis 
show that there was an increase of from approximately 600,000 per 
gram when fresh to approximately 93,000,000 per gram when air- 
dried for 14 days. At the end of that time the organisms were still 
sufficiently active to grow readily on litmus-lactose-asparagin agar. 
It is easy to understand, therefore, how milk produced under clean 
conditions may become contaminated with organisms of the B. coli 
type. Contamination by this means, however, is not serious from 
the standpoint of numbers introduced, because the small numbers that 
enter from the air are greatly diluted in the milk. 
Table 4. — Direct increase of colon count in dried cow feces. 
Number of 
days dried 
at 70° F. 
(21.1° C). 
Moisture. 
Colon 
count, wet. 
Colon 
count, dry. 
(fresh)... 
2 
Per cent. 
84.5 
79.0 
6.3 
5.0 
Per gram. 
320, 000 
1,500,000 
49, 000, 000 
89, 000, 000 
Per gram. 
590, 000 
2, 685, 000 
51,940,000 
93, 450. 000 
10.. 
14 
