32 SCIENCE PROGRESS. 



which have the appearance of typhoid bacilli will not grow. 

 At all events the turbidity of formalin-bouillon is decisive 

 against the presence of bacillus typhosus. 



Since formalin is only a saturated solution of formyl 

 aldehyde in water, Schill has also examined the anti-bacterial 

 action of this gas. He states that exposure for seventy 

 minutes not only inhibits but kills bacillus typhosus, while 

 bacterium coli commune and typhosus-like water bacteria 

 preserve their vitality after an exposure of over two hours ; 

 a longer period inhibits their activity though this is re- 

 covered in twelve hours when the action of the vapour is 

 abolished. Under no circumstances does Eberth's bacillus 

 recover after similar treatment. Interesting as these de- 

 tails are, they do not really mark an advance on earlier 

 methods for differentiation such as those employed by 

 Chantemesse and Widal (21), by Parietti and others, where 

 cultivations upon media such as carbol-bouillon, methyl- 

 violet gelatine or fuchsin-agar are largely relied upon as a 

 means of diagnosis. 



During the last few years numerous investigators have 

 been occupied in the study of the chemical changes which 

 media show during the growth of these bacteria. Papers 

 by Kiessling (36), Pere (34), Blachstein (32), Germano and 

 Maurea (15) and Dunbar (1 7) all indicate that the differential 

 diagnosis between Eberth's and Escherich's bacteria must 

 be sought for in the chemical changes which the medium 

 undergoes. 



It is allowed that some well-defined differences between 

 the typhoid bacillus isolated from the spleen and the bacterium 

 coli commune taken from the bowel do exist, and though 

 Rodet and Gabriel Roux (22) consider that the latter is 

 capable of being transformed into the specific microbe of 

 typhoid fever this view has found more opponents than 

 defenders. The chief points of interest in differential 

 diagnosis may be referred to here. 



That gases are developed when Escherich's bacterium 

 is grown upon weak alkaline bouillon to which two per cent, 

 of dextrose or lactose is added was noticed by Th. Smith (23) 

 in 1889. Independently Chantemesse and Widal (24) made 



