448 



MALTA FEVER 



Cultivation. This can usually readily be effected by making 

 stroke cultures on agar tubes from the spleen pulp and incub- 

 ating at 37 C. The colonies, which are usually not visible 

 before the third or fourth day, appear as small round discs, 

 slightly raised and of somewhat transparent appearance. The 

 maximum size 2-3 mm. in diameter is reached about the 

 ninth day ; at this period by reflected light they appear pearly 

 white, while by transmitted light they have a yellowish tint in 

 the centre, bluish white at the periphery. A stroke culture 

 shows a layer of growth of similar appearance with somewhat 



serrated margins. Old 

 cultures assume a buff tint. 

 The optimum temperature 

 is 37 C., but growth still 

 occurs down to about 20 

 C. On gelatin at summer 

 temperature growth is ex- 

 tremely slow after two or 

 three weeks, in a puncture 

 culture, there is a delicate 

 line of growth along the 

 needle track and a small 

 flat expansion of growth 

 on the surface. There is 

 no liquefaction of the 

 medium. In bouillon there 

 occurs a general turbidity 

 with flocculent deposit at 

 the bottom ; on the surface 



there is no formation of a pellicle. The reaction of the media 

 ought to be very faintly alkaline, as marked alkalinity interferes 

 with the growth. On potatoes no visible growth takes place 

 even at the body temperature, though the organism multiplies 

 to a certain extent. Outside the body the organism has 

 considerable powers of vitality, as it has been found to sur- 

 vive in a dry condition in dust and clothing for a period of two 

 months. 



Eelations to the Disease. There is in the first place ample 

 evidence, from examination of the spleen, both post mortem and 

 during life, that this organism is always present in the disease. 

 The experiments of Bruce and Hughes first showed that by 

 inoculation with even comparatively small doses of pure cultures 

 the disease could be produced in monkeys, sometimes with a 

 fatal result. And it has now been fully established that inocula- 



FIG. 153. Micrococcus raelitensis, from a 



two days' culture on agar at 37 C. 



Stained with fuchsin. x 1000. 



