No abstract

The present Standard Methods agar for the bacterial plate count of dairy products, so-called T.G.E.M. agar (Tryptone, 0.5 percent; dextrose, 0.1 percent; beef extract, 0.3 percent; skim milk, 1.0 percent; and agar, 1.5 percent), has been in use for more than 10 years.' This medium, called the standard medium in this report, was fonnulated when attempts were made to obtain a more productive agar than the official standard medium existing at the time. It fulfilled this purpose and was adopted. That it is not an ideal medium is attested by a number of persons who use it routinely.The disadvantages stem from the presence of two ingredients.One of the ingredients, skim milk, gives rise to several difficulties.In the first place, it takes skill to add skim milk to the medium successfully in the form of dissolved dried powder. Second, after being added to the medium, milk sometimes exhibits a tendency to settle out when the medium is held in a tempering bath prior to pouring. Finally, and perhaps most important, milk induces cloudiness in the agar which, although seeming to make colonies stand out more distinctly at times, actually tends to make counting more difficult.This difficulty is due to the selection which the eye must make between very fine particles of milk and fine colonies. There is little question that, as a rule, colonies on a clear medium are more easily counted. During the experimental work presented here, technicians experienced in the use of the standard medium volunteered the information that the new milkless media studied caused less eyestrain.A second objection to the present standard medium is the presence of a nonstandardized product, beef extract. The best information

No abstract

THIS is the second report on the study of bacteria in the air of several types of locations in New York City. The first, a brief preliminary note,' was read before this section in 1936.The previous report summarized the findings as to average numbers of total bacteria and of alpha and beta streptococci, in 6 types of locations, during the first 16 weeks of the study. The present paper continues and elaborates the analysis of the findings, as to alpha streptococci, only, for an entire calendar year. The probable origin of the alpha streptococci found is also discussed, as well as the appearance, numerical frequency, and possible significance of certain variant forms.

This study was carried out at the request of the Standard Methods Committee of the American Public Health Association. It offers a suggestion for a uniform procedure.