516 EXPERIMENTAL RESEARCHES WITH CHICKEN-CHOLERA MICROBES, 



As liquid medium for the cultivation of these microbes I em- 

 ployed rabbit-flesh infusion, in the following briefly termed rabbit- 

 broth, or simply broth. Stated in a few words, this liquid was pre- 

 pared by allowing finely minced flesh of well-nourished, thoroughly 

 healthy, wild rabbits to stand with double the quantity (in 

 weight) of distilled water, in a cool place, for twenty-four hours, 

 stirring up from time to time, filtering and pressiug through 

 cheese-cloth, steaming, filtering again, neutralising with 20 p.c. 

 watery solution of anhydrous carbonate of soda, or rather pro- 

 ducing a slightly alkaline reaction, steaming and filtering again, 

 and ultimately filling into different-sized, cotton-wool-plugged, 

 sterilised test-tubes, which with their contents were thereupon 

 discontinuously sterilised. 



In such plain rabbit-broth, without any additional ingredients, 

 the chicken-cholera bacteria grow very luxuriantly at a suitable 

 temperature ; they grow in that medium with pretty much the 

 same vigour as in rabbit-broth to which 1 p.c. dry peptone and 

 0'5 p.c. sodium chloride are added. Broth of the latter description 

 I employed, besides the former, in connection with certain experi- 

 ments {re Immunisation, p. 526). 



Of nutrient solid soils I mostly used a 6 p.c. rabbit-broth-pep- 

 tone-gelatine, which was prepared in the usual way, with the 

 difi"erence that infusion of rabbit-flesh instead of beef -infusion was 

 taken. On such a rabbit -broth -gelatine, the chicken-cholera 

 microbes flourish excellently ; fully developed stick-cultures always 

 showed a substantial, expanded, superficial layer, of a whitish 

 colour and sticky structure. The colour of the growth along the 

 stick-canal, at first also whitish, changed into yellowish or yellowish- 

 brown in old cultures ; the same applied to isolated colonies in the 

 gelatine. 



In nutrient agar-agar — in the preparation of which beef- 

 infusion was used — I saw the superficial growth (in stick- 

 cultures) assume the shape of a thin film extending nearly 

 over the whole surface, while the stick began to show by and 

 by a darker coloration than the slightly yellow agar. 



