240 BACTERIA PATHOGENIC TO MAN 



Pathogenesis. The lesions present in intestinal infection are those 

 of enteritis ; the duodenum and jejunum are found to contain fluid, the 

 spleen is somewhat enlarged, and there is marked hyperaemia and ecchy- 

 mosis of the small intestines, together with swelling of Peyer's patches. 



Intraperitoneal and intravenous inoculation of guinea-pigs and rab- 

 bits may also produce death, which, when it follows, usually takes 

 place within the first forty-eight hours, accompanied by a decided fall 

 of temperature, the symptoms of enteritis, diarrhoea, etc., and finally 

 fibropurulent peritonitis. 



When subcutaneous inoculations of mice and guinea-pigs are made 

 it requires the introduction of much larger quantities of the cultures 

 to produce infection; in rabbits this is followed only by abscess forma- 

 tion at the point of inoculation. Dogs and cats are similarly affected. 



Albarran and Halle* have caused cystitis and pyelonephritis by direct 

 injections into the bladder and ureters, the urine being artificially sup- 

 pressed; Chassin and Roger produced angiocholitis and abscess of the 

 liver in the same way. Akermann produced osteomyelitis in young 

 rabbits by intravenous injections of cultures. 



From experiments on animals it would, therefore, appear that the 

 true explanation of the pathogenesis of the colon bacillus is undoubt- 

 edly to be found in the toxic effects of the chemical substance and 

 products of the cells. 



Immunization. Immunization against colon bacillus infection is pro- 

 duced in the same way and to the same degree as in typhoid bacillus 

 infection. The serum from a horse receiving a number of different 

 strains is required, if protection from all members of the colon group 

 is desired. The serum is not at present employed therapeutically. 



Occurrence in Man and Animals during Health. The bacillus coli 

 communis is a common inhabitant of the intestinal canal in man and 

 in almost all domestic animals. It is also found at times in wild animals 

 and appears at times to develop in fishes. 



Occurrence Outside of the Intestines. Colon bacilli are found wherever 

 human or animal feces are carried. In water a very few colon bacilli, 

 less than one to each 10 c.c., are not sufficient to give rise to the sus- 

 picion that it is contaminated. Even 1 per c.c. does not show human 

 contamination, since such a number could equally well come from manure 

 spread on fields. Colon bacilli are apt to be found in everything which 

 comes in contact with man or animals, or dust where they have been. 



Variation in Morphological and Biological Characters. By subjecting 

 them to higher than normal temperature, to long growth in old culture 

 fluids, to the action of weak antiseptics, and to the passage through 

 animals, colon bacilli have been changed so as to lose the power to make 

 indol and ferment sugars with gas production. They have not, however, 

 been made to approach typhoid bacilli in their agglutination charac- 

 teristics or in their motility. The change has simply been to weaken the 

 characteristics typical of colon, and this gives them appearances similar 

 to typhoid bacilli, but in parasitic ways they are still quite different. 



To the colon group the following characteristics are essential : short 



