May 22, J914] 



SCIENCE 



767 



age pollution. It is, therefore, seen tbat although 

 the total number of these organisms is about the 

 same in either supply, there are nearly twice as 

 many B, coli-like organisms in the supply subject 

 to greater sewage pollution than in the Gunpowder 

 Eiver. 



Notes on the Bcu;teriology of Air and Its Sani- 

 tary Significance: C.-E. A. Winslow. 

 Both mouth spray and dust contain buccal bac- 

 teria and at times pathogenic forms, and might 

 theoretically constitute sources of appreciable at- 

 mospheric pollution. Whether they actually do so 

 or not can only be determined by quantitative 

 studies of the bacteria actually present in air and 

 particularly of the characteristic organisms of the 

 mouth. Two sets of results bearing upon this 

 point are here reported. 



A series of 684 examinations of school room air 

 in New York City made by Professor Chas. Bas- 

 kerville and the writer gave an average of 96 

 microbes per cubic foot. This includes all organ- 

 isms developing on litmus lactose agar in five 

 days at room temperature. Two hundred and 

 sixty-eight samples gave counts under 50, 178 be- 

 tween 51 and 100, 112 between 101 and 150, 39 

 between 151 and 200, 23 between 201 and 250, 12 

 between 251 and 300, and 17 over 300. Lactose 

 fermenting streptococci (characteristic buccal 

 forms) were found 52 times in 174 cubic feet of 

 air giving an average of 30 per 100 cubic feet of 

 air. 



The second series of results includes 64 samples 

 of outdoor air (mainly from New York City 

 streets) examined in the course of a somewhat de- 

 tailed study of air bacteriology now being car- 

 ried on by the New York State Commission on 

 Ventilation. The average 20° count of 64 samples 

 was 59 microbes per cubic foot. Twenty-four 

 samples sho-wed less than 25, 18 between 26 and 

 50, 8 between 51 and 100 and 14 over 100. The 

 maximum count was 395. At 37° in two days the 

 average count was 48 microbes per cubic foot. 

 Thirty-six samples were below 26, 9 between 26 

 and 50, 9 between 51 and 100 and 7 over 100. 

 Acid forming streptococci were absent from 12 

 cubic feet of air examined for their presence. 



The Usefulness of Dried Stained Smears of Milk 

 03 a Means of Determining the Sanitary Qual- 

 ity of Milk: Egbert S. Breed .\nd James D. 

 Brew. 

 A number of tests of the method of making 



milk smears devised by Prescott and Breed* have 



i Journal of Infectious Diseases, 7, p. 632, 1910. 



been made at the Geneva Experiment Station with 

 a view of determining the sanitary quality of 

 milk. It has been found to be a very rapid and 

 efficient method of determining the total germ 

 content where milk contains 100,000 or more bac- 

 teria per c.c. The results secured probably rep- 

 resent the real conditions so far as total content 

 is concerned better than those secured on agar or 

 gelatin plates. By means of this test it is pos- 

 sible to separate milk as received at a milk sta- 

 tion into two classes by a rapid examination of 

 the prepared smears. The first grade of milk is 

 that in which no bacteria are seen in 5 to 10 or 

 more fields of the microscope. In all but eight of 

 the sixty samples in which no bacteria were found 

 the agar plate count was less than 100,000 per 

 c.c. and seven of the eight which exceeded this fig- 

 ure were less than 200,000 per c.c. Such milk 

 would sell in the New York City market as Grade 

 A, selected pasteurized if properly pasteurized. 

 Inasmuch as a laj'ge proportion of the milk re- 

 ceived at the particular milk station where the 

 tests were made was of this quality this test would 

 have been used to great advantage because it 

 would have enabled the dealer to raise this part of 

 his milk from Grade B to the Grade A class at no 

 expense to himself or to the farmers supplying the 

 milk except the cost of making the tests, which is 

 fortunately not great enough to be prohibitive. 



The second class of milk would be that in which 

 bacteria are readily found with the microscope. 

 Such milk under present regulations would go on 

 the market as Grade B milk if properly pasteurized. 

 The great advantage of this test over plate meth- 

 ods of examinations or other bacterial methods 

 that require an incubation period, is that results 

 can be secured in a very few minutes and a large 

 number of samples can be handled by a single per- 

 son. Any person sufficiently skilled to handle a 

 microscope can learn the technique and apply the 

 method successfully. The chief weakness of the 

 method at present is that it is so new and has 

 been tried out so little in a practical way that no 

 one knows as yet how the results secured should 

 be interpreted. The bacterial counts obtained are 

 much higher than those obtained from the ordi- 

 nary plate counts and there is no constant relation- 

 ship between such counts where single compari- 

 sons are made. When a long series of compari- 

 sons are made between plate counts and these 

 microscopic counts, it is found that greater dis- 

 crepancies occur when the total number of bac- 

 teria is low than when the total number of bac- 

 teria is high. A detailed report on this work will 



