ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 717 



and nitrate-forming bacteria were put in Erlenmeyer flasks. To these 

 flasks were added coke from experimental contact beds, soil from irriga- 

 tion field, etc., in quantities of a few grains. The solutions were kept 

 at 25° C. to 26° C, and examined daily for ammonia, with Nessler'* 

 reagent ; for nitrites, with sulphanilic acid and a naphthol ; and for 

 nitrates, with diphenylamine. After six days sub-cultures were made, 

 and from these inoculations were made on silica jelly. By such means 

 organisms were isolated agreeing completely with Winogradsky's Nitroso- 

 monas and Nitrobacter. 



Identification of the Bacillus typhosus in Stools.* — E. Klein and 



A. C. Houston, from a research on this subject, conclude that the 

 Drigalski-Conradi medium in plates incubated at 87° C. is of value in 

 assisting detection in a short time (24 hours) of the presence of B. coli 

 communis and allied forms ; the colonies of this microbe being noticeable 

 by their red colour. Accordingly, in the search for the Bacillus typhosus 

 in stools the above colour reaction permits of many colonies being ex- 

 cluded. The recognition of the typhoid colonies was found possible 

 only in the plates made with high dilutions ; and in these alone were 

 the (red) colonies of B. coli sufficiently reduced in number to allow 

 recognition of the typhoid (blue) colonies. Tests with sub-cultures are 

 necessary. It follows, therefore, that where the typhoid bacilli are 

 present in a stool only in small numbers the Drigalski plate is not able 

 to demonstrate them with certainty, for the reasons that : the method 

 does not alter the initial proportion of B. coli to B. typhosus ; high 

 dilution of the stools is necessary ; all blue colonies are not those of 



B. typhosus. \\. 



Bacteriological Test for Estimating Pollution of Air.f — M. H. 

 Gordon has undertaken an inquiry to determine whether it is possible 

 to find a bacteriological test of the pollution of air by material given 

 off from the human body, comparable to the B. coli (etc.) test for the 

 pollution of water by material derived from a like host : a test capable 

 of application as an index of the possible access of morbific virus to 

 air in a manner similar to that in which the B. coli (etc.) test is an 

 index of its possible access to water. Air is liable to be polluted by 

 material given off from the human body in the acts of expectoration, 

 coughing, sneezing and speaking, and such material consists of mucus 

 derived from the respiratory passages. The procedure adopted was : 

 (1) A bacterial analysis of a number.of samples of saliva obtained from 

 normal individuals was made, special attention being paid to the micro- 

 organisms most abundant therein, with the object of determining 

 whether any particular micro-organism is by the abundance and con- 

 stancy of its presence characteristic in the way that B. coli is charac- 

 teristic of fasces. The most abundant and constant organism in normal 

 saliva was found to be Streptococcus brevis of Lingelsheim. The sparse 

 occurrence of bacilli was noticeable. Neutral-red broth, for the reason 

 that its colour is markedly changed by S. brevis, is, when incubated 

 anaerobically for 48 hours at 37° C, a culture test whereby very minute 



* Rep. Med. Off. Local Govt. Board, 1902-3, pp. 622-46. 

 t Tom. cit., pp. 421-71. 



