394 THE COLON BACILLUS 



SECTION I. EXPERIMENTAL INOCULATION. 



The colon bacillus is [usually] pathogenic to guinea-pigs, rabbits, mice ; 

 and other animals. Though often avirulent when isolated from the stools 

 of healthy persons, its virulence can be rapidly increased by passing it through 

 the peritoneal cavities of a series of guinea-pigs. Guinea-pigs are the most 

 suitable animals for the study of the experimental disease. 



A virulent strain may easily be obtained by suturing the anus of a guinea-pig. 

 The animal dies of intestinal obstruction, and a pure culture of a very virulent colon 

 bacillus can be isolated from the cloudy peritoneal exudate. Should the exudate 

 as is sometimes the case contain a few other organisms mixed with the colon bacillus, 

 a pure culture of the latter can be readily obtained by plating on gelatin. 



Sub-cutaneous inoculation of a colon bacillus of low virulence into guinea- 

 pigs, rabbits or mice leads, as a rule, to the formation of an abscess 

 which resolves spontaneously. Intra-peritoneal inoculation produces a more 

 severe, but not usually fatal infection. 



The inoculation of a virulent strain, on the other hand, usually gives rise 

 to an acute disease in these animals : the effects will be described in detail. 



1. Guinea-pigs, (a) Intra-peritoneal inoculation. The inoculation of a 

 few drops of a broth culture into the peritoneal cavity causes death in about 

 20 hours with symptoms of sub-acute peritonitis and a sub-normal tem- 

 perature. Post mortem, there is a generalized peritonitis with a copious, 

 turbid exudate : the coils of the intestine are covered with a purulent fibrinous 

 exudate : the lumen of the gut is rilled with diarrhoeal matter, the walls are 

 swollen and congested and occasionally show some mucous ecchymoses, the 

 Peyer's patches are swollen and the spleen enlarged ; in females the organs 

 of generation are congested and it is not uncommon to find the uterus filled 

 with an hsemorrhagic exudate. The organism can be isolated from the 

 blood and internal organs. 



(P) Intra-pleural inoculation. Death supervenes in 24 hours. Post 

 mortem there is an excess of fluid, sometimes blood-stained, in the pleura, 

 with fibrinous deposit on the lungs, pericardial effusion, congestion of the 

 lungs and intestine and swelling of the spleen. The bacillus is present in the 

 blood and internal organs. 



(y) Sub-cutaneous inoculation. This leads to a less severe infection than 

 the preceding and much larger doses of culture (1-2 c.c.) are required to pro- 

 duce a fatal result. A swelling forms at the site of inoculation, the bacillus 

 becomes disseminated and death takes place in 48 hours. Post mortem the 

 Peyer's patches and the spleen are swollen and the intestine congested and 

 ecchymosed. 



2. Mice. Mice, though less susceptible, succumb to the inoculation of 

 cultures of the bacillus. The lesions are similar to those in guinea-pigs. 



3. Rabbits. Eabbits also are less susceptible than guinea-pigs, and much 

 larger doses must be used to produce death ; post mortem the lesions are 

 similar in the two cases. 



When a small dose is inoculated sub-cutaneously the animal does not die 

 for several days and post mortem suppurative foci will be found in the liver, 

 spleen and mesenteric glands. 



Intra-venous inoculation usually leads to a rapidly fatal infection ; the 

 rabbit suffers from a colon bacillaemia resulting in the production of the usual 

 lesions in the walls of the intestine and spleen. 



Sometimes the animal may survive the intra- venous inoculation of a few drops of 

 a broth culture for several months. In such cases an atrophic paralysis appears as 



