l6o UNIVERSITY OF COLORADO STUDIES 



ten hours a very rapid increase of germs — especially of the lactic acid 

 type. This interdependence of germs of entirely different character- 

 istics is known as microbic association or, in this instance, as the asso- 

 ciative action of bacteria in milk. 



Let us consider these various samples of milk from the standpoint 

 of a food for infant feeding. It is generally accepted that such a 

 milk should not show a greater number of germs per cubic centimeter 

 than 10,000. A perusal of Chart I will show that only five of the 

 twenty-one samples show a count under 10,000. Of these No. 3 

 and No. 4 are from a private cow. The milk was drawn into a thor- 

 oughly clean jar and every means of prevention of contamination 

 was observed. No. 6 was from a general dairy, and throughout 

 showed a remarkably clean milk. No. 7 is from a private dairy 

 furnishing thirty-five famihes. This milk is poured into pails at the 

 producer's house and delivered in those pails to the consumer. No. 8 

 showed a low initial count with high acidity and loppered quickly, 

 a circumstance which leads me to think it was dirty milk which was 

 pasteurized after the germs had developed, which would give a low 

 count and high acid reaction. This milk could hardly be recom- 

 mended raw for infant feeding. This leaves then only four milks of 

 the twenty-one examined, or only three of eleven different dairies, which 

 could be used unpasteurized for infant or invalid feeding. Such a 

 condition of affairs, of course, would not be bad for a city where of 

 necessity there must be a time interval of a good many hours between 

 the milking and delivery to the consumer. In a small town like 

 Boulder, however, such a time interval is not necessary. Now let 

 us consider these milks from the standpoint of the general consumer — 

 not necessarily for infant or invalid feeding. 



Some cities have adopted an arbitrary standard. I wrote to the 

 Health Department of about thirty cities of varying sizes to determine 

 what, if any, was the standard accepted as fair and reasonable for 

 such a city. I found that in ten of these cities such a standard had 

 been adopted and Chart V shows the standards and the population 

 of each place. These cities require that any milk sold within their 

 boundaries shall not exceed a certain number of germs. For Boston 



