480 A MANUAL OF BACTERIOLOGY 



the reaction is positive, the 1 in 200 dilution of the patient's serum 

 shows clumping within half an hour, and the 1 in 400 dilution 

 after two hours, but the 1 in 800 dilution shows no clumping. 



Complement fixation is stated to be of service in the late stages 

 of the disease, when it is difficult or impossible to detect bacilli 

 and a diagnosis is desired. 



In the examination of rats suspected to be suffering from plague 

 infection, it is essential not only to take the naked-eye characters 

 into account, but to make microscopical preparations and cultures, 

 and to test the cultures by animal inoculations. Care must be 

 taken not to mistake hcemorrhagic septiccemic bacilli (see pp. 468, 481 ) 

 and other organisms for the plague bacillus. The B. coli, B. proteus, 

 and other organisms are recorded by Klein (loc. cil.) as simulating 

 the J5. pestis. 



Chicken Cholera 



Chicken cholera is a disease of poultry characterised by profuse 

 diarrhoea ; its course may be very rapid, and the bird found dead 

 without having shown signs of illness. The organism (B. [Pasteur- 

 ella] cholerce-gallinarum, B. avisepticus) is a very short rod, non- 

 motile, so short that it is almost ovoid, 0-6 to 0-8 /LI in length, and 

 0-4 to 0-5 /Z in diameter. It stains by the ordinary anilin dyes, 

 but not by Gram's method, and the staining tends to be polar, so 

 that Pasteur, who first investigated the disease, described it as a 

 diplococcus (Plate XVI, a). It is aerobic and facultatively 

 anaerobic, non-sporing, and is easily killed by heat and antiseptics. 

 The organism grows freely on the various culture media from 20 

 to 38 C., 011 agar forming a thick, moist, cream-coloured layer, 

 on gelatin a shining, white, expansive growth without liquefaction. 

 In broth a general turbidity forms, but growth on potato is 

 indifferent. Some strains appear to produce acid only, other 

 strains acid and gas, from most of the sugars. If dried it dies in 

 a few days, but retains its vitality for a considerable time in damp 

 earth or in water, and so infection is readily conveyed. Fowls die- 

 after subcutaneous, intramuscular or intravenous inoculation and 

 by feeding, the organisms being found abundantly in the blood. 

 Post-mortem, the serous membranes may be inflamed and hsemor- 

 rhagic, the liver large and soft, and the intestine shows haemor- 

 rhagic spots, and is sometimes ulcerated and contains a mucoid 

 fluid stained with blood. Other birds, pigeons, pheasants, spar- 



