CHAPTER XVI. 



MALTA FEVER; MUMPS; RELAPSING FEVER; 

 WHOOPING-COUGH. 



Micrococcus Melitensis. 



IN 1887 Bruce succeeded in isolating a micrococcus from 

 the spleen, liver, and kidneys of persons suffering from Malta 

 fever. The injection of pure cultures of this organism into 

 animals produced the disease, thus establishing its specificity. 

 It also agglutinated with the serum of Malta fever patients. 



Morphology and biology : Micrococcus melitensis measures 

 about 3 p. in diameter and usually occurs singly. Chains are 

 never formed. It stains well with an aqueous solution of 

 gentian-violet, but not by Gram's method. It exhibits 

 Brownian movement, but not actual motility. 



The organism grows well on agar-agar at the body tem- 

 perature, forming very minute round translucent colonies, 

 which do not become confluent. The growth is not apparent 

 until after forty-eight hours. In the gelatin stab and agar 

 stroke the development is the same as on the plate, but the 

 colonies gradually increase in size until they finally form a 

 rosette-like mass. The track of the needle shows a brownish 

 growth with serrated edges. If the tube containing the 

 growth is examined by transmitted light, the centre of the 

 colonies composing the growth is yellowish in color and the 

 periphery bluish-white. By reflected light the entire colony 

 is milky in appearance. 



The growth in gelatin is always imperceptible. The 

 medium is not liquefied. There is no growth on potato. 



The natural habitat of this germ and the method of infec- 

 tion are unknown. It is always found in the organs of 

 Malta fever cadavers, and can also be obtained in pure cult- 



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