CULTURAL CHARACTERS. 411 



blood-stained and foul-smelling, there being a great proportion 

 of other organisms present besides the cholera spirilla (Koch). 



Cultivation. (For Methods, see p. 426.) 



The cholera spirillum grows readily on all the ordinary media, 

 and with the exception of that on potato, growth takes place at 

 the ordinary room temperature. The most suitable temperature, 

 however, is that of the body, and growth usually stops about 

 16 C, though in some cases it has been obtained at a lower 

 temperature. 



Peptone Gelatin. On this medium the organism grows well 

 and produces liquefaction. In puncture cultivations at 22 C. a 

 whitish line appears along the needle track, at 

 the upper part of which liquefaction commences, 

 and as evaporation quickly occurs, a small bell- 

 shaped depression forms, which gives the appear- 

 ance of an air-bubble. On the fourth or fifth day 

 we get the following appearance : There is at the 

 surface the bubble-shaped depression ; below this 

 there is a funnel-shaped area of liquefaction, the 

 fluid being only slightly turbid, but showing at 

 its lower end thick masses of growth of a more 

 or less spiral shape (Fig. 141). The liquefied 

 portion gradually tapers off downwards towards 

 the needle track. (This appearance is, however, 

 in some varieties not produced till much later, 

 especially when the gelatin is very stiff, and, in 

 other varieties which liquefy very slowly, may 

 not be met with at all.) At a later stage, lique- 

 faction spreads and may reach the side of the 

 tube. 



In gelatin plates the colonies are somewhat FIG. 141. Punc- 

 characteristic. They appear as minute whitish ture culture of the 



cholera spirillum m 



points, visible in twenty-four to forty-eight hours, peptone gelatin 

 which, under a low power of the microscope, do NaturKzeT ^" 

 not present a smooth circular outline, but one 

 which is irregularly granular or furrowed ; as they become larger 

 their surface has an appearance which has been compared to 

 fragments of broken glass. Later, liquefaction occurs, and the 

 colony sinks into the small cup formed, the plate then showing 

 small sharply marked rings around the colonies (Fig. 142). 



