448 THE PASTEURELLA GROUP 



and Palmipedse (ducks and geese). Rabbits though very susceptible to 

 experimental infection are rarely attacked by the epizootic disease. 



The course of the disease may be rapid and its onset sudden. Usually however 

 it is not so acute, and the animals, after being miserable and drowsy and suffering 

 from an attack of diarrhoea, often hsemorrhagic in character, die in 5-7 days. The 

 sick birds do not feed, they droop their wings, their feathers are dull and bristling 

 and their combs black. Towards the end of the outbreak the cases become less 

 severe and some of the birds recover. 



Infection takes place via the alimentary canal by means of food contaminated 

 by the dejecta of birds suffering from the disease. The organism is found in the 

 blood, internal organs and intestines in acute cases, but it is impossible to find it in 

 chronic cases. 



SECTION I. EXPERIMENTAL INOCULATION. 



Animals may be infected by inoculating them with a few drops of a 

 24-hour-old culture, or with the blood of an animal which has just died of 

 fowl cholera, either sub-cutaneously or intra-peritoneally or in the case of 

 birds in the pectoral muscle. 



To produce infection in animals by feeding the food may be watered with 

 a virulent culture or they may be fed upon the tissues of an animal which has 

 died of the disease. 



1. Susceptible animals. Birds generally and especially small birds (sparrows, 

 etc.) are very susceptible ; they may be infected in various ways, though 

 feeding often fails to produce the disease. 



Rabbits are particularly susceptible to the fowl pasteurella, and may be 

 easily infected by feeding or by sub-cutaneous inoculation. They die in the 

 very early stages of the disease, before diarrhoea has had time to manifest 

 itself, though on post mortem examination the intestine is found to be full 

 of liquid matter. This fact affords an explanation of the rarity of the epizootic 

 disease among rabbits, the excreta being the ordinary vehicle of infection. 



Post mortem the stomach is distended, the blood black and hsemolyzed ; 

 there are numerous effusions of blood and the pleurae on both sides are 

 affected. 



Mice and rats are very susceptible, and the ground squirrel should be 

 mentioned among rodents susceptible to the disease. It was at Metchni- 

 koff's suggestion that the bacillus of fowl cholera was used to start true 

 epizootics among ground squirrels in order to diminish their numbers in 

 parts of Southern Russia which were infested with them. 



Guinea-pigs are fairly immune. The inoculation of a moderate dose of a 

 virulent culture into the sub-cutaneous tissues does not kill the animal, but 

 merely produces an abscess ; the pus from the abscess contains but few micro- 

 organisms but is nevertheless virulent for fowls. Guinea-pigs however 

 generally succumb as a result of the injection of a virulent culture into the 

 peritoneal cavity ; and if a given culture be passed from animal to animal 

 in this way its virulence can be increased sufficiently to kill a guinea-pig on 

 sub-cutaneous inoculation. 



Dogs and cats are only slightly susceptible ; sub-cutaneous inoculation 

 produces a swelling which quickly subsides and the animal recovers ; intra- 

 venous inoculation is followed by more severe results and may prove fatal. 

 By passage through a series of dogs or cats the virulence of the organism 

 for the species is considerably increased, and sub-cutaneous inoculation will 

 then prove fatal. 



Pigs are only slightly susceptible to sub-cutaneous inoculation but often 

 die after intra- venous inoculation. 



