30 SCIENCE PROGRESS. 



the spores of anthrax bacilli so that these appear to each 

 contain a nucleus, finds that under similar treatment the 

 typhoid bacillus and bacterium coli commune only exhibit a 

 simple beaded appearance which has nothing of the nature of 

 spore formation. 



Since morphological characters and micro-chemical re- 

 actions do not furnish sufficient criteria for the determination 

 of the identity of bacillus typhosus, considerable attention 

 has been given to the behaviour of this bacillus upon various 

 culture media ; this microbe is not capable of transference 

 to animals, and therefore this method of diagnosis, which is 

 absolute for the bacteria of such diseases as anthrax or 

 glanders, is excluded. Some observers have published cases 

 of an experimental typhoid fever which follows the introduc- 

 tion of bacillus typhosus into the peritoneal cavity of mice 

 and guinea pigs, but the condition which is established by 

 this method appears to be due to an intoxication with the 

 products of the metabolism of the bacterial culture rather 

 than to a distribution of the microbes in the infected animals 

 that is in any sense comparable with the mode in which the 

 specific bacilli of typhoid fever are found to spread in the 

 human body. In connection with this question the recent 

 papers of Sanarelli (13) and others are of great interest. 



Some few years ago the character of bacterial growths 

 on potatoes, in bouillon, gelatine, agar, together with plate 

 •cultivations, played an important part in affording differential 

 characteristics for microbes, and it is beyond question that in 

 some cases a determination of a form is possible by these 

 means alone. Since Gaffky (14) first drew attention to the 

 remarkable growth which bacillus typhosus exhibits on potato 

 this has been held to be typical of this specific microbe. A 

 slightly acid reaction of the medium, however, appears 

 necessary, and E. Fraenkel and Simmonds were the first to 

 point out that on many varieties of potato an obvious dirty 

 grey growth occurred, instead of the almost invisible film 

 which is so peculiar. Many observers, and among these 

 Germano and Maurea (15), consider the growth on potato 

 •of little value as a diagnostic sign ; and the observations of 

 Fuller (16) are interesting, since he isolated no fewer than 



