EXPERIMENTAL INOCULATION 553 



of the tissues is broken down and the phagocytic action of the leucocytes hindered, 

 with the result that a septicsemic condition develops. Leclainche and Vallee 

 obtained in this way cultures very virulent for the species, 3 c.c. of which sub- 

 cutaneously injected was sufficient to cause death. 



Mice, rats, dogs, pigs, cats and birds are immune. 1 



2. Methods of infection. 



The Bacillus chauvcei being a strict anaerobe only grows when inoculated, 

 deeply into the tissues, and does not infect superficial wounds. 



The influence of the site of inoculation is very marked. The same dose 

 of the virus which will kill an ox when inoculated into the cellular tissues of 

 the body will set up merely a benign infection if inoculated into the con- 

 nective tissue of the neck. 



In the latter case however if the inoculated part be warmed the bacillus 

 will multiply and the animal may die. 



The influence of temperature is emphasized by the fact that frogs under normal 

 conditions resist infection but succumb to the disease if kept in the incubator at 25 C. 

 after being inoculated. 



The inoculation of a virulent virus into the veins of an ox merely leads to 

 a temporary rise of temperature : but if at the time of inoculation a trace 

 of the virus gain access to the peri vascular tissues a fatal septicaemia ensues. 

 Infection may also be established by rupturing a blood vessel after intra- 

 venous inoculation (Arloing). 



The disease may be produced experimentally in several ways : 



(i) By the inoculation of cultures. If ordinary cultures be inoculated the 

 result will be uncertain, but if young cultures in Martin's broth be used 

 infection will certainly follow : three or four drops inoculated beneath the 

 skin will kill a guinea-pig (500 grams) in 18-24 hours (Leclainche and Vallee). 



(ii) By inoculation of infected blood. Blood from the heart of a guinea-pig 

 or sheep recently dead of the disease should be sealed up in pipettes, incubated 

 for 48 hours and then used for inoculation. 



(iii) By inoculation of serous exudates. Method recommended. The fluid 

 from the local oedemata may be inoculated without heating : take a portion 

 of one of the swellings and crush it up in a mortar with a little sterile water 

 and inoculate the emulsion. The dried exudate (Arloing's powder, vide 

 infra] may also be used : in this case grind up a little of the powder with a 

 few drops of sterile water and add a trace of lactic acid. 



(iv) By inoculation of spores alone. By applying methods similar to those 

 described in the chapter on malignant oedema (Chap. XXXVIII.), Leclainche 

 and Vallee have shown that the inoculation of spores free from toxin does not 

 lead to the death of the animal : but the spores, like those of the bacillus of 

 malignant oedema, will, if protected from the action of the phagocytes, 

 germinate and originate a fatal disease ; certain substances and certain 

 organisms (e.g. Staphylococcus aureus) will also assist the germination of the 

 spores and so favour infection. 



3. Symptoms and lesions. 



The disease produced experimentally in the guinea-pig will be taken as 

 the type. 



If the material be inoculated into the muscles of the thigh a painful and 



1 It has been suggested that the bacillus of malignant oedema and the bacillus of quarter 

 ill are identical species. This position however cannot be maintained, for apart from 

 morphological and cultural differences, they differ widely in their pathogenicity ; all 

 the animals which have just been mentioned as immune to the latter bacillus are suscep- 

 tible to the bacillus of malignant oedema. 



