GERMS IN RELATION TO MILK 27 



which was cold and rainy. The great increase of germs when milk 

 is kept at improper temperatures, we have already noticed, the 

 number of germs in such milk depending entirely upon its age. To 

 show the effect of dust and unclean utensils on milk I may cite the 

 following: A sample of pasteurized milk, taken from a delivery 

 wagon and examined by the writer, contained seven million germs, 

 while from the same wagon was also taken a sample of the same 

 milk put into sealed milk bottles which contained but 24,000 germs 

 to the cubic centimeter. The first sample was taken from a large 

 can which was frequently opened to pour out small quantities for 

 consumers and very likely the can was unclean before the milk was 

 put into it. 



After the milk is withdrawn from the cow the number of 

 germs in it generally diminishes for a longer or shorter time, 

 and after this period the number rapidly increases. Thus at forty 

 degrees the number of germs may not be greater in thirty or forty 

 hours than it was when the milk was first withdrawn. At a higher 

 temperature the germs begin to multiply in the milk as soon as the 

 third hour after it has left the cow. Each variety of germ has a 

 special temperature at which it flourishes to best advantage. The 

 lactic acid germs grow more favorably at comparatively high tem- 

 peratures- — from 70° to 90 F., or even higher. 



There are certain special germs — not all of which have been 

 studied — which produce special faults, or, as they have been called, 

 diseases of milk. 



Thus the butyric acid germs develop that acid by the splitting 

 tip the fat in rancid butter. Yellow, red, blue, brown and green 

 milk are rarely seen and the particular coloration is due to changes 

 produced in the milk by special germs. A turnip taste is often 

 given milk by a particular germ (B. fcetidus lactis). So also are 

 slimy milk, bitter, stringy and soapy milk, owing to special germ- 

 development and its effect on milk. It is thought that slimy milk 

 may be caused by cows eating the leaves of the plant, Pinguicula. 

 "vulgaris, since placing the leaves in milk will induce this condition. 



