GENERAL SYSTEMATIC BACTERIOLOGY 243 



That the Malta fever and contagious abortion organisms are closely related 

 was confirmed by Fleischner, Meyer and Shaw in 1919, and later by a number of 

 other investigators. Meyer and Shaw (1920) proposed the generic name 

 "Brucella," in the family Bacteriaceae to include the Malta fever and contagious 

 abortion organisms. That name has met with general approval, and has been 

 used by foreign investigators (Khaled, Archibald). 



Meyer and Shaw did not, however, give a generic diagnosis for the genus 

 Brucella, and they did not consider other species besides the melitensis-abortus 

 group which would logically belong to the new genus. They were apparently 

 unaware that Castellani and Chalmers had already described a newly created 

 genus, "Alkaligenes," which, according to its definition, would include the tneli- 

 tensis-abortus group. The definition is as follows: "Bacillaceae growing well on 

 ordinary laboratory media; not forming endospores; aerobes, and often facultative 

 anaerobes; without fluorescence, pigment formation, or gelatin liquefaction; 



without polar staining; Gram-negative, without a capsule Milk 



not clotted; glucose and lactose not fermented." The type species of the genus 

 "Alkaligenes" as established by "original designation," is A. faecalis, a common 

 intestinal saprophyte. Castellani and Chalmers left the "Micrococcus meliten- 

 sis" unclassified generically — "Incertae sedes" — because they were doubtful as 

 to whether it should be considered a coccus or a rod form. 



Bacteriological nomenclature is passing through an experimental, transitional 

 stage, and criteria which should serve for valid specific or generic distinctions 

 have not been established in detail. The characteristics which are available at 

 present for bacterial classification are few; they are more or less variable accord- 

 ing to varying conditions; and they are not well correlated. Hence comes the 

 difficulty in classifying bacteria into a system comparable with that of the higher 

 organisms. It appears that, in many cases, distinction must be made by means 

 of the sum total of differences, rather than by differences in particular stable 

 characteristics, such as obtains in the classification of higher organisms. 



If melitensis is considered cogeneric with faecalis, then the Law of Priority 

 demands the acceptance of the generic name Alkaligenes. If, however, the differ- 

 ences between the two species are sufficient for generic distinction, the valid name 

 of the genus is Brucella. The writer is of the opinion that a generic distinction 

 should be made between the organisms under discussion, which are characteristic- 

 ally invaders of the tissues of animals, and the type species of Alkaligenes, which 

 is characteristically a saprophyte. Morphologically, also, melitensis is readily 

 distinguished irova faecalis by its smaller size and by its great numbers of coccoid 

 cells. 



There is given herewith a general description of melitensis, the type species of 

 the genus Brucella: 



Minute rods with many coccoid cells ; (the cells of two-day cultures grown on 

 the surface of plain agar and stained with carbol fuchsin appear about 0.5 of a 

 micron wide and 0.5 to 2 microns long); not forming endospores; non-motile; 

 aerobic, or preferring a slightly reduced, partial pressure of oxygen; without 

 gelatin liquefaction; Gram-negative; parasitic, invading animal tissues; neither 

 gas nor acid production from the carbohydrates. 



Other species, which vary somewhat from the foregoing description, will logi- 

 cally be allocated to the genus Brucella. This genus should include a variety of 



