14 BUL-LETIN 739, U. S. DEPARTMENT OF AGRICULTURE. 



It is believed that the results shown in Table 7 cover the analyses 

 of fresh milk produced under the widest range of conditions generally 

 met with in the commercial production of milk. The conditions of 

 production ranged from clean barn and cows and sterilized utensils 

 to extremely dirty conditions and unsterilized utensils not washed 

 till 8 hours after milking. The colon counts produced under such 

 circumstances should represent the maximum number of these 

 organisms usually introduced into milk. 



The results on this point are considered so important that they 

 have been plotted in figure 1. The graph shows the percentage of 

 samples in which the colon count was 100 per cubic centimeter or 

 more, as well as the percentage with lower counts. The letters cor- 

 respond to those in Table 7; therefore the conditions of production 

 are not repeated. Within each column is shown the colon count of 

 every sample having 100 or more per cubic centimeter. Column A 

 represents milk of high quality from a bacterial standpoint, only a 

 small percentage of the samples showing the presence of organisms 

 of the colon-aerogenes group in 1/100 of a cubic centimeter. A number 

 of these samples were examined for the presence of the colon-aerogenes 

 group in yg- of a cubic centimeter, but none were found. Much larger 

 amounts of milk of this quality would probably have to be examined 

 in order to obtain positive tests. 



Column B represents milk produced under extremely dirty barn 

 conditions with sterilized utensils. This is a condition which would 

 rarely be encountered because a dairyman who kept his barn and 

 cattle in as dirty a condition as they were in this experiment probably 

 would not be the kind who would take the trouble to sterilize utensils. 

 This condition is, nevertheless, one of interest because only about 10 

 per cent of the samples produced under it showed the presence of the 

 colon-aerogenes group in 1/100 of a cubic centimeter. 



Column C represents results obtained from milk produced under the 

 same dirty conditions as previously described, but the utensils were 

 not sterilized. Milk produced under this condition represents, in a 

 bacterial sense, more nearly the average milk of poor quality, but 

 even then the condition of the barn and cattle was worse than is 

 usually found. The term "dirty conditions" merely presents to the 

 reader a degree of filth, and therefore depends upon his own opinion. 

 It is believed, however, that the reader will be convinced of the degree 

 of filth under which the milk was produced by referring to Plates I 

 and II, where sediment disks from 1 pint of milk handled in un- 

 sterilized small-top and open pails under the filthy conditions men- 

 tioned are shown. One must admit that the quantity of manure 

 shown on most of the sediment disks is greater than that usually 

 found in milk. The illustrations show, besides the total bacterial 

 count, the colon count per cubic centimeter in samples where they 



