SIGNIFICANCE OF COLON COUNT IN MILK. 33 
3. High colon counts can nearly always be attributed to the growth 
of organisms originally introduced into milk. Little or no growth 
of the organisms of the colon-aerogenes group occurs below 50° F. 
(10° C), but rapid growth takes place at higher temperatures. 
4. The differentiation of the B. coli and B. aerogenes types does not 
assist materially in tracing the conditions under which milk is pro- 
duced, but future results from a greater number of samples may 
show that it is of some value. 
5. In fresh milk the colon count does not indicate the extent of 
direct manurial contamination, but does indicate the general condi- 
tions of cleanliness under which the milk was produced. 
6. In milk of unknown history no significance can be attached to 
the colon count other than that high counts usually indicate that 
it has been held above 50° F. (10° C), or rarely, that it was produced 
under very abnormal conditions, as previously described. 
7. A careful study of the limitations of the colon count as an index 
of cleanliness in milk production, taking into account especially the 
effect of temperature on the growth of the organisms, will materially 
assist the laboratory man in makin the colon count serve to the 
best advantage. 
