14 BUL-LETIX 739, U. S. DEPARTMENT OE 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 duty 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 ^o 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 duty 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 
