NOT DESCRIBED IN PREVIOUS SECTIONS. 533 



injected subcutaneously or into the peritoneal cavity of rabbits or 

 guinea-pigs, a fatal termination depends largely on the quantity in- 

 jected ; and although the bacillus may be obtained in cultures from 

 the blood and the parenchyma of the various organs, it is not present 

 in large numbers, and death appears to be due to toxaemia rather than 

 to septicaemia. Mice are not susceptible to infection by subcutaneous 

 injections. Small quantities injected beneath the skin of guinea-pigs 

 usually produce a local abscess only ; larger amounts two to five 

 cubic centimetres frequently produce a fatal result, with symptoms 

 and pathological appearances corresponding with those resulting 

 from intravenous injection. These are fever, developed soon after 

 the injection, diarrhoea, and symptoms of collapse appearing shortly 

 before death. At the autopsy the liver and spleen appear normal, or 

 nearly so ; the kidneys are congested and may present scattered 

 punctiform ecchymoses (Weisser). According to Escherich, the 

 spleen is often somewhat enlarged. The small intestine is hyper- 

 aemic, especially in its upper portion, and the peritoneal layer pre- 

 sents a rosy color ; the mucous membrane gives evidence of more 

 or less intense catarrhal inflammation, and contains mucus, often 

 slightly mixed with blood. In rabbits death occurs at a somewhat 

 later date, and diarrhoea is a common symptom. In dogs the subcu- 

 taneous injection of a considerable quantity of a pure culture may 

 give rise to an extensive local abscess. 



In human pathology the colon bacillus plays an important role. 

 It is concerned in the etiology of a considerable proportion of the 

 cases of cystitis and of pyelonephritis, and peritonitis resulting from 

 perforation. It appears to be the cause of certain affections of the 

 anal region (Hartmann and Lieffring). It has been obtained in pure 

 culture from abscesses in various parts of the body, from the valves 

 of the heart in endocarditis, from the pleural cavity in empyema, etc. 

 It has also been found in the blood, as a result of general infection 

 following cystitis and pyelonephritis (Sittmann and Barnow). 



Varieties. Booker, in his extended studies relating to the bac- 

 teria present in the faeces of infants suffering from summer diarrhoea, 

 has isolated seven varieties " which closely resemble Bacterium coli 

 commune in morphology and growth in agar, neutral gelatin, and 

 potato, but by means of other tests a distinction can be made between 

 them." 



Some of the pathogenic bacteria heretofore described are also 

 closely allied to the " colon bacillus " and by some bacteriologists are 

 supposed to belong to the same group i.e., to be varieties of the 

 same species rather than independent species with fixed characters. 

 Whatever may be the remote relationship, the typhoid group, the hog- 



