EXPERIMENTAL INFECTION 489 



SECTION I. THE EXPERIMENTAL DISEASE. 



1. Choleraic peritonitis. 



The inoculation of a culture of the cholera vibrio into the peritoneum of 

 a guinea-pig generally leads to a rapidly fatal peritonitis (Pfeiffer) ; but this 

 experimental peritonitis has no analogy whatever with the intestinal disease 

 of man. 



Vibrios from different sources differ widely in their virulence for the same 

 animal species. Thus some vibrios which are not derived from cases of 

 cholera in man will produce peritonitis in guinea-pigs, while others only 

 recently isolated from the intestine of a person suffering from cholera may 

 prove absolutely harmless to these animals. 



There seems to be no relationship between the power of a vibrio to set up choleraic 

 peritonitis in guinea-pigs and its ability to produce intestinal cholera. 



To produce choleraic peritonitis in the guinea-pig scrape the growth from a 

 young agar culture, rub it up in a little sterile broth and inject the, emulsion 

 into the peritoneal cavity. A few hours later the animal becomes drowsy, 

 the temperature falls below normal, collapse sets in and is followed by con- 

 vulsions and death. Post mortem there is considerable fluid in the peritoneal 

 cavity in which a variable but small number of vibrios can be found : the 

 intestine is distended and pink in colour, and the bacillus will be found in 

 small numbers in its contents : there will be no visible lesions of the viscera. 

 The vibrio may gain access to the blood stream. 



The virulence of a vibrio may be increased by passage through the peritoneal 

 cavities of guinea-pigs, but after passage through about twenty animals the 

 virulence of the exalted virus appears to be fixed (Haffkine) and cannot be 

 further increased. 



2. Choleraic septicaemia. 



Infection of guinea-pigs and rabbits by sub-cutaneous inoculation can 

 only be effected when very virulent strains are used. In such cases the animal 

 dies more or less rapidly from choleraic septicaemia, death being preceded by 

 a fall of temperature, convulsions and collapse : the blood and viscera yield 

 pure cultures of the vibrio. Ground squirrels are much more susceptible to 

 inoculation with the cholera vibrio than guinea-pigs. 



Intra-muscular inoculation appears to produce more severe symptoms 

 than sub-cutaneous inoculation. Intra-venous inoculation produces in 

 rabbits symptoms like those of cholera with lesions in the intestines (bluish 

 red in colour with desquamation of the mucous membrane), while the organism 

 is found in large numbers in the contents of the intestine, blood and viscera 

 (Kolb and Issaeff). 



Pigeons. Non-pathogenicity for pigeons was for a long time thought to be 

 one of the characteristic features of the cholera vibrio. This however is not the 

 fact for Gamaleia and Metchnikoff have shown that many undoubted cholera 

 vibrios are pathogenic for these birds ; the Angers vibrio, for instance, if 

 inoculated into the pectoral muscles of pigeons will produce a rapidly fatal 

 septicaemia. 



3. Intestinal cholera. 



The symptoms following sub-cutaneous or intra-venous inoculation of the 

 cholera vibrio are very different from those characteristic of asiatic cholera 

 in man. Attempts to infect animals by the alimentary canal failed to pro- 

 duce satisfactory results until the subject was taken up by Metchnikoff ; as 

 a result of his experiments a considerable advance was made in the study 

 of experimental intestinal cholera. 



