EXPERIMENT STATION REPORTS. 189 



SUMMARY. 



When pljitiiig methods are used, no one medium should be expected 

 to give results which indicate correctly the condition of all grades of 

 juilk. 



The pH score proved more efficient as a means of detecting slight 

 changes in the history of milk than did the plating methods tried. 



The methods as a whole were efficient in detecting slight changes in 

 'the history of the samples as follows : 



In samples with bacterial counts under 25,000 — 45.8% efficient. 



In samples with bacterial counts between 25,000-100,000 — 71.4% 

 efficient. '^ 



In samples with bacterial counts between 100,000-1,000,000— 85.0% 

 efficient. 



In samples with bacterial counts over 1,000,000 — 97.0% efficient. 



It seems that the medium giving highest average counts depends upon 

 the predominant groups present in the sample studied. This may ac- 

 count for divergent results obtained by various workers. 



REFERENCES. 



1. Cooledge, L. H. and Wyant, E. W. — ^The Keeping Quality of Milk as 

 Judged by the Colorimetric Hvdrogen-ion Determination. Journal 

 of Dairy Science, Vol. Ill, Ko.'2, March, 1920. 



Cooledge, L. H. — The Colorimetric Hydrogen-ion Determination as 

 a Means of Stu<lying Biological Changes in Dairy Products. Tech- 

 nical Bulletin No. 52, Michigan Agricultural College Experiment 

 Station, November, 1921. 



C4ioledge, L. H. and Coodwin, O. T. — An Experiment in Improving 

 the Milk Supply of a City Milk Plant. Special Bulletin No. 112, 

 Michigan Agricultural College Experiment Station, November, 

 1921. 



2. Boiling, Geo. E. — ^Keport of Committee on Methods of Bacterial 

 Analyses of Milk and Milk Products. Tenth Annual Report and 

 Eleventh Annual Report, International Association of Dairy and 

 Milk Inspectors, 1921, 1922. 



3. Ayers, S. Henry and Mudge, C. S. — ^Milk-Pow^ler Agar for the De- 

 termination of Bacteria in Milk. Journal of Bacteriology, 5, No. 6, 

 November, 1920. 



[L. H. COOLEDGE.] 



In connection with tlie Avork of Research Associate Huddleson, I 

 wisli to make a rec()mm('ndation that has a far-reaching significance. 

 Immediate steps should be taken to provide for all experimental work 

 on animal diseases in a manner that meets the needs of the projects and 

 at the same time conserves the interests of the sections of Dairy, Animal 

 and Poultry Husbandrv. It is not alone the work with infectious abor- 

 tion but also that on poultry diseases and parasitic infestations that 

 demands suital)1e housing. Now tliat the direction of this work has 

 been centralized it seems opportune to make adequate provision for all 

 the work. 



