THE FOWL PASTEURELLA 449 



Sheep are susceptible, and succumb rapidly to the intra- venous inoculation 

 of a highly virulent culture ; with a less virulent virus the animal dies only 

 after an interval of some days, having in the meantime suffered from a 

 multiple purulent arthritis. 



2. Symptoms and lesions. The symptoms in the fowl will be described, as 

 this is the animal most frequently used for experimental purposes. The 

 disease in the rabbit has already been described. 



A few drops of a virulent culture will kill fowls in 12-30 hours. In fulminat- 

 ing cases there are practically no symptoms ; if however the animals live long 

 enough the symptoms are the same as in the spontaneous disease : at 

 first the animal is unsteady and swells itself out, its feathers are ruffled and 

 its comb black, then purging begins and the dejecta are mucous or blood- 

 stained : finally the fowl becomes drowsy and comatose and death follows 

 a series of convulsions. When inoculated with a less virulent virus the 

 animal may recover from the disease or die after the lapse of several days 

 with cachexia and arthritis of its hind limbs. 



Post mortem, at the site of inoculation, there is a very small quantity 

 of blood-stained oedema rich in bacilli. If the inoculated virus were only 

 slightly virulent the oedema is more marked, and when the disease lasts 

 for several days the infiltration is gelatinous, the pectoral muscle around 

 the site of inoculation is swollen and yellowish in colour and may even have 

 a lardaceous appearance (necrosis). The blood is black, coagulates feebly 

 and has the appearance of being hsemolyzed, and contains the pasteurella 

 in enormous numbers. The sub-cutaneous cellular tissues, the serous mem- 

 branes and internal organs all show haemorrhages : the lungs contain foci of 

 infiltration, the liver is large, yellowish and friable, and the spleen swollen 

 and softened. These last-named lesions are not however constant. The 

 pericardium contains a clear serous fluid sometimes blood-stained or gela- 

 tinous ; and a similar effusion is found in the pleural cavities in rabbits (birds 

 do not possess a pleural cavity). The muscles and the heart are only affected 

 if the disease has lasted several days ; in that case they are soft and yellowish 

 like a dead leaf. The intestine presents the lesions of enteritis, the mucous 

 membrane being injected and ulcerated in patches. The intestinal contents 

 are fluid and sometimes blood-stained. When the virus inoculated is only 

 slightly virulent and death is delayed, arthritis 

 of the joints of the posterior limbs can often be 

 demonstrated on post mortem examination (Lig- 

 nieres). 



As usual, the lesions are more marked the 

 longer the animal lives. 



SECTION II.- MORPHOLOGY. 

 1. Microscopical appearance. 



The fowl pasteurella is a small bacillus or cocco- 

 bacillus. The length does not exceed 0'5-1'25/A 

 and the breadth 0'25-0'40/a. In unstained pre- 

 parations the organism has the appearance of ^th, Reich.) 

 more or less elongated points refractile in the 



centre and often arranged in pairs : it exhibits active Brownian movement 

 but no movement of translation. In stained preparations, which are the 

 best for a study of the morphology of the bacillus, it is seen to be oval 

 in shape with rounded ends, and when lightly-stained preparations (thionin) 



