A STUDY OF BACTERIA IN MILK 71 



EXERCISE XXII 



A STUDY OF BACTERIA IN MILK 



104. It is desirable to understand somewhat clearly the 

 bacterial contents of milk and to know something of the 

 physiological properties of these bacteria. For this reason 

 it is desirable to study though but briefly the bacteria in 

 ordinary market milk. 



References. Russell, Dairy Bacteriology; also one by Conn 

 and one by Grotenfelt. Hunziker, Germicidal action in cow's milk, 

 Bulletin No. 197, Cornell Univ. Exp. Station. Ward, The inva- 

 sion of the udder by bacteria, Bulletin No. 1 78, Ibid. Park, Bac- 

 terial contamination of the milk of our cities, The N.Y. Univ. 

 Bulletin of the Med. Science, Vol. I. Moore, Bacteria in milk. 

 Report of the Com. of Agriculture of N.Y., 1902. 



105. Work for this exercise. Examine the plate cultures made 

 from milk. Describe the different kinds of colonies and state 

 approximately the number of each. Examine microscopically 

 the bacteria in one of each kind of colony and determine its 

 genus. 



Inoculate a tube of milk and one of gelatin from each of 

 three different kinds of colonies, stating the genus of the 

 bacteria in each. 



Inoculate Group A of media from a culture of B. prodigiosiis 

 furnished. 



Make for examination at the next and following exercises 

 three gelatin plates from a sample of water furnished (unfil- 

 tered creek or well water), using for each culture the quantity 

 designated by the instructor. The quantity will depend upon 

 the condition of the water. 



