NOMENCLATURE 815 



Nomenclature. — We have no space to discuss the early confusion of terminology 

 that existed over members of this group. The whole position was altered when 

 Evans in 1918 drew attention to the essential similarity of the organisms which 

 at that time were described as Micrococcus melitensis and Bacillus abortus. Nor 

 do we propose to discuss the validity of the generic name Brucella suggested for 

 them by Meyer and Shaw (1920) and by Feusier and Meyer (1920) in honour of 

 Sir David Bruce. This is so appropriate and has met with such universal approval 

 that no other term seems likely to enter into serious competition with it. There 

 are, however, certain points that require discussion. The three organisms isolated 

 from goats, cattle, and pigs respectively are so closely allied that their differentiation 

 can be accomplished only with difficulty. The question is, therefore, whether they 

 should be regarded as varieties of one species, or should be ranked as separate 

 species. Both proposals have their advocates. On the whole we favour the latter 

 course, mainly for the sake of convenience. We shall therefore refer to these three 



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Fig. 171. — Brucella abortus. Fig. 172. — Brucella melitensis. 



From an agar culture, 24 hours, 37° C, From an agar culture, 2 days, 37° C, showing 

 showing very short bacillary forms ( X 1000). mainly coccal forms ( X 1000). 



organisms as Br. melitensis, Br. abortus and Br. suis. It must be pointed out, 

 however, that the differences between the American and Danish porcine types are 

 almost as great as those between the porcine and bovine types, and the decision 

 to treat them as varieties of Br. suis is purely arbitrary. 



The names paramelitensis, para-abortus, and parasuis are frequently used to 

 refer to inagglutinable strains of Brucella, corresponding most closely to the meli- 

 tensis, abortus, and suis types. So long as the so-called para-strains were regarded 

 as distinct species, no objection could be raised to this terminology ; but now 

 that they are known to be merely rough variants of the original smooth forms, 

 this practice is no longer justifiable and merely serves to confuse the nomenclature. 

 We shall refer to these, therefore, as rough melitensis, abortus, or suis strains, as 

 the case may be. 



The inclusion of J5r. tularensis in this group is largely tentative. Reimann (1932), 

 along with several other workers, would assign it to the Pasteur ella group on account 

 of its bipolar staining, its solubility in 1/800 sodium ricinoleate, and its transmission 

 by insect vectors. On the other hand its general morphology, the beneficial effect 



