CHAPTER VIII. 



BACTERIOLOGICAL EXAMINATION OF MILK. 



Numerical determination of bacteria. The diversity of 

 methods in use in different laboratories is such that compari- 

 son of the numerical results obtained by them is quite out of 

 the question. The water bacteriologists long ago recognized 

 the undesirability of a diversity of methods in counting bac- 

 teria in water, and applied a remedy. The standard methods 

 of water analysis suggested by the committee of the American 

 Public Health Association have been favorably received. The 

 results warrant and encourage further work towards the unifi- 

 cation of other laboratory methods. A committee of the Lab- 

 oratory Section of the American Public Health Association 

 has in hand the task of formulating standard methods of bac- 

 terial milk analysis. The committee, consisting of F. H. Slack, 

 chairman ; W. H. Park, E. C. Levy, F. C. Harrison, C. E. 

 Marshall and H. Iv. Russell, has been at work for two years, 

 weighing the merits of the various methods in use. There 

 have been submitted two preliminary reports, one in 1907 and 

 one in 1908 (3, 4). The methods reported are not definitely 

 selected as a final standard, but represent a consensus of opinion 

 of American workers on the subject. The methods for the 

 numerical determination of bacteria herewith recommended 

 are a composite of the two reports of the A. P. H. A. Com- 

 mittee. The recommendations are substantially as made in 

 the 1907 report, and the modifications made in 1908 are intro- 

 duced and so indicated. 



NUMERICAL DETERMINATION OF BACTERIA. 



There is no method known by which the exact number of bacteria 

 in a sample of milk may be determined, and even when the best methods 



