550 PATHOGENIC MICROORGANISMS 



are susceptible, and the disease produced in these animals is in many- 

 features identical with that of man. 



Transmission seems to take place chiefly by the ingestion of infected 

 milk. Direct cutaneous infection or through mucous membranes may 

 also occur. In human beings, suffering from the disease, the organisms 

 may be isolated from the blood stream during the entire course of 

 the disease and as early as the second day. The disease is rarely 

 fatal, death occurring in less than 2 per cent of the cases (Eyre, loc. cit.)} 



The microorganism causing the disease was isolated in 1887 by 

 Bruce,^ a British army surgeon. 



Morphology. — Micrococcus melitensis is a minute bacterium ap- 

 pearing coccoid in smears from agar cultures, in broth cultures assum- 

 ing the form of a short, slightly wedge-shaped bacillus resembhng B. 

 influenzae. Babes ' regards it as unquestionably a bacillus. Eyre de- 

 scribes it as a minute coccus, and believes the bacillus-like individuals 

 to represent involution forms. It appears in irregularly parallel groups, 

 and occasionally forms short chains. 



It is easily stained with the ordinary dyes, and is decolorized by 

 Gram's method. 



Cultivation. — Micrococcus melitensis can usually be cultivated from 

 the spleens of those who have succumbed to the disease and from the 

 blood stream in active cases. It grows on nutrient agar at 37.5° C, 

 forming small, pearly white colonies at the end of two or three days. 

 It grows easily on all of the ordinary laboratory media. 



Both in patients and in injected animals, infection with this bacte- 

 rium produces specific agglutinins which are of great practical aid in 

 diagnosis.^ 



' British Commission Report cited from Eyre in Kolle und Wassermann, 

 Handbuch, etc., Erganzungsband, Heft 2. 

 ^ Brvux, Practitioner, 1887. 

 ^ Babes, KoUe und Wassermann, iii, p. 443. 

 * Wright and Lamb, Jour. Path, and Bact., v, 1899. 



