NOT DESCRIBED IN PREVIOUS SECTIONS. 467 



cholera group, the Bacillus typhi murium of Loffler, the bacillus of 

 Laser, the Bacillus euteritidis of Gartner, and other similar bacilli 

 appear to be differentiated from one another by characters which 

 justify their description under separate names. Still it is difficult to 

 fix upon any one of these characters to which specific value can be 

 attached ; and, in view of the many varieties found in nature or pro- 

 duced artificially in laboratory experiments, we are not justified in 

 asserting that our classification of these low organisms has any sub- 

 stantial scientific foundation. The difficulties attending an attempt 

 to establish specific characters are well illustrated by the extensive 

 literature relating to the differentiation of bacilli belonging to the 

 typhoid group from those belonging to the colon group. The main 

 points upon which the distinction must depend have been referred to 

 in the section devoted to the typhoid bacillus. 



Fremlin (1893) has made a comparative study of the colon bacil- 

 lus from various sources. He finds the common characters of gas 

 production in media containing sugar and coagulation of milk. Cul- 

 tivated from different animals the morphology is the same, but there 

 are differences as regards motility. The most active movements are 

 said to be exhibited in the bacillus from man, while the variety ob- 

 tained from the intestines of rabbits showed scarcely any movements. 

 The different varieties displayed considerable differences in their 

 growth upon potato. 



Dreyfuss (1894) finds decided differences in the pathogenic viru- 

 lence of the colon bacillus from healthy individuals and from those 

 suffering from various intestinal disorders. A culture from the dis- 

 charges of a fatal case of cholera nostras proved to be exceptionally 

 virulent tested by intraperitoneal injections in guinea-pigs. Gilbert 

 (1895), as a result of his extended researches, concludes that there are 

 five principal types among the bacilli most nearly related to the colon 

 bacillus: 1st. Bacilli which differ from the colon bacillus by their 

 being non-motile. This type includes two varieties : one gives thick 

 yellowish colonies upon gelatin plates and numerous gas bubbles on 

 potato this is the bacille lactique of Pasteur and the Bacillus lactis 

 aerogenes of Escherich ; the other gives thin, bluish-white colonies 

 and includes the bacille de rendocardite of Gilbert and Lion. 3d. 

 Bacilli which differ from the colon bacillus by the fact that cultures 

 do not give the indol reaction. 3d. Bacilli which do not cause the 

 fermentation of lactose. 4th. Bacilli which are not motile and 

 do not ferment lactose. 5th. Bacilli which are not motile, do not 

 give the indol reaction, and do not ferment lactose. 



Theobald Smith (1895) gives the following account of his method 

 of detecting bacilli of the "colon group " in water : 



