408 CHOLERA. 



all.) At a later stage, liquefaction spreads and may reach 



the side of the tube. 



In gelatine plates the colonies are somewhat characteristic. 

 They appear as minute whitish points, 

 visible in twenty - four to forty - eight 

 hours, which, under a low power of 

 the microscope, do not present a smooth 

 circular outline, but one which is ir- 

 regularly granular or furrowed ; as they 

 become larger their surface has an ap- 

 pearance which has been compared to 

 fragments of broken glass. Later, lique- 

 faction occurs, and the colony sinks into 

 the small cup formed, the plate then 

 showing small sharply - marked rings 

 around the colonies (Fig. 108). Under the 

 microscope the outer margin of the cup 

 is circular and sharply marked. Within 

 the cup the liquefied portion forms a 

 ring which has a more or less granular 

 appearance, whilst the mass of growth 

 in the centre is irregular and often 

 broken up at its margins. Later still, 

 liquefaction spreads around and the 

 appearance becomes less characteristic. 

 The growth of the colonies in gelatine 

 plates constitutes one of the most im- 



cuUureTf Ae'cholera P 0rtant meanS f distinguishing the 



spirillum in peptone cholera spirillum from other organisms, 

 gelatine six days' On the surface of the a^ar media 

 ize " a semi-transparent greyish white layer 

 forms, which presents no special char- 

 acters. On solidified blood serum the growth has at first 

 the same appearance, but afterwards liquefaction of the 

 medium occurs. On agar plates the superficial colonies 

 under a low power are circular discs of brownish-yellow 

 colour, and more transparent than those of most other organ- 

 isms. On potato at the ordinary temperature, growth does 



