42 UNIVERSITY OF WISCONSIN STUDIES 



although the real germ content was vastly higher in the sour 

 milk. It should be noted that this is a comparison of the 

 results from individual plates and that the average from a 

 considerable number of simultaneous plate determinations 

 gave more logical results. A study of the above data by Dr. 

 Reitz showed that the results of approximately twenty-five 

 simultaneous plate determinations should be averaged to give 

 results which are satisfactorily accurate. :JG Ordinary labora- 

 tory studies are made with four to six simultaneous plates 37 

 but routine municipal determinations are frequently based 

 upon the count from single plates. In the face of the demon- 

 strated variability of bacterial plate counts, the use of the 

 results from single plates in municipal laboratories is ex- 

 tremely unsatisfactory. 



Another stumbling block in the way of bacterial plate 

 standards is the fact that there are so few municipalities 

 equipped with men and facilities for making as accordant 

 plate counts as those discussed above. The number of cities 

 in the United States thus properly equipped is considerably 

 less than the number which have already adopted such muni- 

 cipal standards. Any standard of keeping quality which 

 is to be a satisfactory aid in measuring the keeping quality 

 of city milk must be much more widely applicable than 

 standard bacterial plate counts are at present. The "little 

 plate" method suggested by Frost 38 meets some of these ob- 

 jections but as yet has not been commonly employed. 



The direct microscopic estimation of the bacteria in milk 

 has a number of advantages over the plate count among which 

 are the quickness with which it can be made and the relatively 



:!G Data presented by H. L. Reitz and H. A. Harding to the Laboratory 

 Section of the Amer. Public Health Association at the Rochester meeting, 

 1914. 



::7 M. J. Prucha and H. M. Weeter, Bui: 199, 111. Agr. Exp. Sta., p. 31, 

 1917. 



:!8 W. D. Frost, Rapid Method of Counting Bacteria in Milk in Sci. 42, 

 pp. 255-256, 1915 ; Comparison of a Rapid MetJiod of Counting Bacteria in 

 Milk with the Standard Plate Method in ./. of Inf. Dis., 19, pp. 273-287, 

 1916 ; A Rapid MetJiod of Counting Bacteria in Milk and Other Richly 

 Seeded Materials in J. Amer. Med. Asso. 66, pp. 889-890, 1916 : Counting 

 the Living Bacteria in Milk A Practical Test in J. of Bact., 2, pp. 567- 

 583, 1917 ; Improved Technique for the Micro or Little Plate Method of 

 Counting Bacteria in Milk in J. of Inf. Dis., 28, pp. 176-184, 1921. 



