372 MICROBIOLOGY OF MILK AND MILK PRODUCTS 



not thrive in the udder. The types of organisms commonly found 

 there do not seem to develop rapidly in the milk when it is held at low 

 temperatures and fail to produce any appreciable changes in it during 

 the normal life of market milk. 



Diseased Udders.- — If, however, the cow is suffering from disease 

 in the udder, the bacterial condition may be quite different from that 

 described above. In this case, the milk may'be filled with the specific 

 bacteria before it leaves the udder. In cases of inflammatory trouble or 

 tuberculosis in the udder the milk may contain very large numbers of or- 

 ganisms, frequently many millions per c.c. at the time the milk is drawn. 



Exterior of Cow's Body. — The nature of the cow's coat and 

 the condition under which she. is normally kept favor the accumulation 

 of dust and bacteria upon her body. Unless special care is taken to 

 keep the cow's biady free from dirt, the organisms which fall into the 

 milk from this source at milking time wiU constitute one of the most 

 important sources of contamination. The importance of this source 

 of contamination may be recognized when we see what large numbers 

 of microorganisms may be carried by small particles of dust or an 

 individual cow hair. 



The importance of this source of contamination depends very 

 largely upon the conditions under which the cows are kept and the care 

 exercised in cleaning just previous to milking. In many of the certified 

 milk'dairies this source of contamination is reduced'to a minimum and 

 has little effect upon the milk. 



Atmosphere of Stable and Milk House. — The atmosphere of 

 the stable is often a very important factor in determining the bacterial 

 content of fresh milk. In sanitary dairies this factor is fully recog- 

 nized and every effort is made to prevent the presence of dust in the 

 atmosphere at the time of milking. The atmosphere is sometimes 

 sprayed either with the hose or with steam in order to settle every 

 particle of dust at milking time. In stables where the importance 

 of this factor is 'not recognized and dust is allowed to exist in the 

 atmosphere at milking time, the number of bacteria in the milk will 

 be materially increased. 



The Milker. — Not infrequently the milker himself is an important 

 source of contamination. If his clothing and hands are dirty or if 

 he brushes ajgainst the cow, the dust thus dislodged may carry into 

 the milk large numbers of microorganisms. This is shown in the dif- 



