NOT DESCRIBED IN PREVIOUS SECTIONS. 



539 



My notes indicate that cultures passed through the guinea-pig are more 

 apt to be motile. 



In gelatin stab cultures the growth of bacillus x resembles that of the 

 colon bacillus, but the colonies at the bottom of the line of puncture are 

 more opaque and not of a clear amber color like that of colonies of the colon 

 bacillus. Upon the surface the growth is thicker than that of the colon 

 bacillus, and forms a milk-white, soft mass. 



The colonies in gelatin Esmarch roll tubes vary considerably at different 

 times. Deep colonies are usually spherical, homogeneous, light brown in 

 color, and more opaque than the similar colonies of the colon bacillus. At 

 the end of a few days the deep colonies become quite opaque, and may be 

 Jobate, like a mulberry, or coarsely granular; sometimes the aeep colonies 

 .have an opaque central portion surrounded by a transparent marginal zone. 



In old gelatin roll tubes these deep colonies form opaque white hemi- 



FIG. 151. FIG. 153. 



Fig. 151. Bacillus cuniculicida Havaniensis; colonies in gelatin roll tube, third day at 20 C. 

 X 6. From a photograph. (Sternberg.) 



Fio. 152. Bacillus cuniculicida Havaniensis ; colonies in gelatin roll tube, end of forty-eight 

 hours. X 10. From a photograph. (Sternberg.) 



spheres projecting from the surface of the dried culture medium, and little 

 tufts of acicular crystals are sometimes observed to project from the side of 

 such old colonies. 



The superficial colonies are circular or irregular in outline, with trans- 

 parent margins a.nd an opaque central portion, sometimes corrugated. They 

 are finely granular and iridescent by reflected light, and of a milk-white 

 color ; by transmitted light they have a brownish color. Young colonies 

 closely resemble those of the colon bacillus. This bacillus grows well at a 

 temperature of 20 C. (68 F.), but more rapidly and luxuriantly at a higher 

 temperature 30 to 35 C. 



It grows well in agar cultures, and especially in glycerin-agar, in which 

 it produces some gas and an acid reaction. The growth on the surface 

 of glycerin-agar cultures is white, cream-like in consistence, and quite abun- 

 dant. 



It grows well in an agar or gelatin medium made acid by the addition of 

 '0.2 per cent (1: 500) of hydrochloric acid. 



In cocoanut water it multiplies rapidly, producing a milky opacity of the 

 previously transparent fluid, an acid reaction, and an evolution of carbon 

 dioxide. 



On potato it produces a thick layer, which may cover the entire surface 

 in three or four days, and which has a dirty-white, cream- white, or pinkish- 



