774 PASTEURELLA 



members of the hsemorrhagic septicaemia group, but that differences in the degree 

 of fixation were usually sufficient to enable strains coming from one animal source 

 to be separated from those from another. Cornelius (1929), by means of the 

 agglutinin-absorption test, classified 17 out of 26 strains of Pasteur ella of diverse 

 origin into 4 groups ; the remaining 9 strains defied classification. Very similar 

 results have been recorded by Yusef (1935) using the precipitation test. Priestley's 

 (1936a, c) observations suggest that Past, septica resembles Past, pestis in forming 

 a heat-labile envelope antigen and a heat-stable somatic antigen. It differs from 

 the plague bacillus in that the envelope antigen appears to be present only in 

 virulent strains, though this requires confirmation ; moreover, the somatic antigen 

 is not the same in all members of the species. Hoffenreich (1928) reported the 

 isolation of a polysaccharide hapten that reacted to high titre with a specific 

 precipitating serum. By means of the trichloracetic acid technique, Pirosky 

 (1938a, c, d) has now extracted from smooth and rough variants four different 

 glycolipoid antigens ; judged by cross-precipitation tests one of these antigens 

 was found to be related to the Vi antigen of the typhoid bacillus, and another 

 to the antigen shared by Salm. typhi and Salm. enteritidis. Unfortunately, 

 the relation between Pirosky's glycolipoid antigens and the envelope and capsular 

 antigens is still far from clear. 



Immune sera can be prepared for all the members by injection of rabbits or 

 horses with living or dead organisms (Haffkine 1905). If living organisms are used, 

 a weakly virulent culture should be chosen for the first few injections. The sera 

 have prophylactic, and to a less extent curative, properties for laboratory animals 

 (Yersin et al. 1895, Chamberland and Jouan 1906). Schiitze's (1932c, 1934) observa- 

 tions suggest that the protective power of a plague vaccine is largely dependent on 

 the presence of the envelope antigen. Working with rats he found that a plague 

 culture grown at 37° C. — a temperature at which the envelope antigen is well 

 developed — was considerably more potent for purposes of immunization than one 

 grown at 26° C. — a temperature which is less favourable for the formation of the 

 capsular material. Moreover, heating of a culture to 100° C. for 15 minutes 

 destroyed the envelope substance and rendered the vaccine useless, while exposure 

 to a temperature of 56° C. for 30 minutes had no such deleterious effect. Sokhey 

 and Maurice (1935), however, working with mice, found that cultures grown at 

 25° C. were as effective as those grown at 37° C. According to Schiitze (1939), 

 the explanation of this discrepancy lies in the relative importance of the two 

 antigens for the type of animal under study. In the protection of rats and guinea- 

 pigs .a large part is played by the envelope antigen, but in mice this antigen appears 

 to be of less importance. 



It has been stated that it is possible, by the use of a pseudotuberculosis vaccine, 

 to immunize rats and guinea-pigs against infection with virulent plague bacilli 

 (MacConkey 1908, McCoy 1911, Eeport 1915). Zlatogoroff (1904), on the other 

 hand, was unable to immunize animals against plague with a pseudotuberculosis 

 antigen, or against pseudotuberculosis with a pestis antigen. He also found that 

 a specific anti-plague serum would protect guinea-pigs against plague, but not 

 against pseudotuberculosis. Boquet (1937) was able, by the use of avirulent 

 bacilli, to protect guinea-pigs against infection with virulent Past, pseudottiberculosis. 



As regards the haemorrhagic septicsemic group, most workers agree that a 

 strain from one animal can be used to vaccinate against infection with strains from 

 other animals (Chamberland and Jouan 1906, Magnusson 1914). A fowl-cholera 



