28 SCIENCE PROGRESS. 



Sanarelli has shown that many varieties or races may- 

 connect these two types, and Metchnikoff (4) believes that 

 these types are not constant forms but simply two races 

 which can easily be transformed the one into the other by 

 causing- them to pass through leucocytes. Multiple varieties 

 of the pneumococci have been demonstrated by Foa, and 

 other micro-organisms have also been shown to possess 

 great flexibility of form. 



According to most bacteriologists the bacterium coli 

 commune, described by Escherich (5) in 1885 as occurring 

 in the excreta of children and animals, is a purely faecal 

 microbe identical with the form discovered by Emmerich (6) 

 in Naples during the cholera outbreak of 1884, and con- 

 sidered by him to be the specific cause of cholera, a view 

 which at once became untenable when it was shown that 

 this micro-organism is constantly present in both the normal 

 and abnormal contents of the bowel, and could also be 

 isolated from air and putrefying liquids (7). It has been 

 remarked that Escherich's bacillus is so ubiquitous and 

 variable in form and cultural behaviour that at the present 

 time it has usurped the position held years ago by bacterium 

 termo. Still the chief interest of bacterium coli commune 

 lies in its pathogenic character and in a morphological 

 resemblance to the bacillus typhosus, which is so marked 

 that the Lyons School hold that the two bacteria are simply 

 harmless and harmful varieties of a common form. Since 

 typhoid fever is undoubtedly propagated by contaminated 

 water or milk, the importance of establishing definite criteria 

 for proving the presence of specific pathogenic microbes in 

 these liquids is evident, and as soon as it becomes possible 

 to recognise the bacillus typhosus in dejecta with the same 

 certainty as the tubercle bacillus can be demonstrated in 

 sputa a great step will be accomplished in the diagnosis of a 

 disease which in its early stages is not always easy of 

 recognition. Aspiration of the spleen and cultivation of the 

 bacillus typhosus from blood obtained by this procedure has 

 been advocated by Redtenbacher (8) and others as a means 

 of diagnosis in doubtful cases of typhoid fever ; and although 

 this operation is stated to be unattended with bad results, 



