404 A MANUAL OF BACTERIOLOGY 



(5) Agglutination reaction. The Indian Plague Commissioners 

 state that in their opinion no practical value attaches to the method 

 of serum diagnosis in plague, but a modified method is considered 

 by Dunbar x to be of considerable value. The method is carried 

 out as follows : 



A small quantity of peptone solution, inoculated with the tissue 

 juice from the suspected organ, is mixed with an equal quantity 

 of plague-serum of such a strength that the dilution reduces it to 

 1 : 200 (approximately). A second dilution of 1 : 400 and a third 

 of 1 : 800 are also prepared. 



As a control, an equal quantity of the inoculated peptone water 

 is mixed with normal serum (rabbit or horse serum), the dilution 

 being 1 : 100. 



In a few minutes a distinct difference is observable. The 

 " control " shows with the oil-immersion lens a few isolated non- 

 mobile bacteria, while the plague-serum dilution 1 : 200 shows 

 larger and smaller masses of agglutinated bacteria. 



After two hours' incubation the same result is obtained with 

 the plague-serum dilution of 1 : 400. No agglutination, however, 

 is observed after incubation for twenty -four hours of the dilution 

 of 1 : 800. This agglutination reaction, in conjunction with other 

 suspicious phenomena, justifies an official notification of suspected 

 plague. 



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 Jicemorrhagic septiccemic bacilli (see pp. 392, 405) and 

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

 other organisms are recorded by Klein (loc. cit.) as simulating the 

 B. 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 is a very 

 short rod, non-motile, so short that it is almost ovoid, 0-6 to 0-8 p 

 in length, and 0-4 to 0-5 p. 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 XV. b). The organism grows 



1 Centralbl.f. Balct,, xli (Originate), 1906, p. 860, 



