86 AIDS TO BACTERIOLOGY 



colon bacillus does. A characteristic fermentation is 

 produced in milk in forty-eight hours: a firm, white, 

 honeycombed curd and a clear, watery whey are produced 

 with abundant gas-formation. The culture is strongly 

 acid, and has a faint, sour smell, like that of butyric acid. 

 Most varieties liberate haemoglobin when grown in broth 

 containing blood (Jordan). When grown anaerobically 

 in undiluted human blood serum with staphylococcus, 

 very copious sporing occurs in two days (Douglas). 

 Fleming recommends neutral-red egg medium for surface 

 growths: in twenty-four hours bright pink spots, 2 milli- 

 metres in size, appear, having slightly raised margins 

 and characteristic prominences in the centres. 



Occurrence. B. Welchii is found in excrernentitious 

 matter and road dust. Its presence in water, milk, shell- 

 fish, etc., is to be regarded as an indication of pollution, 

 not necessarily recent, with faecal matter. 



Pathogenesis. Subcutaneous inoculation of guinea-pigs 

 with recent milk cultures produces in some cases intense 

 spreading hsemorrhagic oedema and necrosis, and death 

 in twenty-four to forty-eight hours. In other cases it 

 is not pathogenic. 



Rabbits are almost immune, but if one be inoculated in- 

 travenously, killed, and the carcass incubated at 37 C. for 

 twenty-four hours, characteristic production of gas follows, 

 especially in the liver (Welch-Nuttall test). B. Chauvoei 

 produces a similar result, but forms spores, while (according 

 to Hewlett) B. Welchii does not under such conditions. 



While the B. Welchii is either absent or rare in the 

 faeces of the young, Kendall has found it in the stools 

 of children with summer diarrhoea. Hewlett thinks it is 

 probably capable of producing necrotic changes in the 

 intestinal mucous membrane, and, because of its abund- 

 ance in the intestine in some cases of primary anaemia, 

 suggests it may have some relation to the condition. It 

 occurs in various pathological conditions, in septicaemic 

 and pyeemic infections of the gastro-intestinal and genito- 

 urinary tracts, and is often responsible for the gas seen 

 in ' foamy organs ' at autopsies. 



In cases of gaseous gangrene occurring among our 

 troops in France B. aerogenes capsulatus (i.e., B. Welchii 

 as originally described by Welch and Nuttall) is dominant 

 in every case. Quinine hydrochloride is found to reduce 



