September 10, 1915] 



SCIENCE 



351 



SOCIETY OF AMERICAN BACTEEIOLOGISTS 

 VI 

 Sanitary Bacteriology 

 Under the supervision of W. W. Ford 

 Bacteria in City, Country and Indoor Air: Wil- 

 liam W. Browne. 



The New Yorli State Commission on Ventilation 

 under the direction of Professor C.-E. A. Winslow 

 undertook a systematic examination of the air in 

 and about New York City. During the survey 353 

 samples of air were examined and may be roughly 

 divided as follows: 



1. City air 134 san 



2. Country air 85 samples. 



3. Office air 87 samples. 



4. Factory air 47 samples. 



The samples were collected and examined ac- 

 cording to the methods proposed by the Committee 

 on Standard Methods for the Examination of Air 

 of the American Public Health Association. In 

 each examination 5 cu. ft. of air were pumped 

 through a sand filter by (1) hand pump in the 

 field, (2) power pump in factories and offices. 

 Samples were plated on gelatin and litmus lactose 

 agar and plated at 20° C. and 37° C, respectively. 



Summary of Results 



Conclusions 



1. Microorganisms developing at 20° C. on gela- 

 tine are generally under 50 per cu. ft., rarely over 

 100 per cu. ft. 



2. Microorganisms developing at 37° C. are 

 rarely over 50 per cu. ft. 



3. Number of Streptococci equals 10 per 100 

 cu. ft. 



4. Air of occupied spaces contains more bacteria 

 than open spaces and shows greater fluctuations. 



1 From Baskerville and Winslow school-room air 

 examination in New York City, in which same 

 methods were employed. 



The Efjiciency of Endo's Medium in Detecting 



Members of the Colon Group: G. C. Supples. 



Fifty-three cultures were studied and identified. 

 Twenty-nine of these were found to belong to the 

 colon group. Eleven were closely allied forms, but 

 could not be included within the group if strict 

 adherence to the classification was observed. Three 

 were coccus forms; four were of the acid pep- 

 tonizing type and two failed to ferment any of 

 the sugars and produced no change in milk. The 

 data were not complete from four of the cultures. 



Eepresentatives of the colon types and the acid 

 peptonizing type were plated upon Endo's me- 

 dium after different degrees of attenuation. The 

 results of these experiments showed that the in- 

 tensity of the reaction was weakened as the at- 

 tenuation increased. The color reaction of the 

 aerogenes and acidi lacti types tended to fade to a 

 white or pink. The fading took place much 

 sooner if the colony developed on the surface or if 

 the culture was at its greatest vigor. 



Since sub-surface development gave rise to many 

 doubtful reacting colonies, two hundred and thir- 

 teen such colonies were studied and fifty-seven per 

 cent, were found not to belong to the colon group. 



From experiments with pure and mixed cul- 

 tures of the colon varieties it was found that about 

 a plus four tenths acidity gave the maximum num- 

 ber of reactions. 



Organisms which Do Not Belong to the Colon 



Group and Produce Bla-cli: Fields on ^sculin- 



Bilesalt Media: J. Vanderleck. 



In the summer of 1913 more than 3,000 sesoulin- 

 agar plates made of milk were examined and 700 

 colonies selected for further study. As a result 10 

 organisms were found to produce black colonies 

 on tesculin-bilesalt media at' blood heat inside 48 

 hours and which did not have the least relation to 

 the colon group. These organisms showed hardly 

 any action in milk, gas production in sugars was 

 absent in the majority and sometimes liquefaction 

 combined with alkalinity was present. These or- 

 ganisms came from one milk district — Huntingdon 

 — and could not be recovered from that source in 

 the following spring. However, another exception 

 appeared for a short time in large numbers. This 

 organism was in many respects closely related to 

 the colon group, produced first acid in milk fol- 

 lowed by alkaline digestion and formed gas in 

 saccharose. Altogether 135 organisms were tested 

 in the examination. 



Working at lower temperature and keeping the 

 plates for at least 5 days, more exceptions would 

 a,ppear, 7 of which were carefully studied. Col- 



