394 MICRO-ORGANISMS AND DISEASE [chap. 



separation is complete, most of the casein flocculi are on 

 the surface mixed with numerous gas bubbles, the cream 

 being so altered that only a thin layer of fluid yellow oil is 

 present on the surface of the culture. Examined under the 

 microscope, the clear whey is full of short cylindrical bacilH. 

 Spore formation in milk cultures is observed only when the 

 culture is made strictly anaerobically and there is no marked 

 spontaneous evolution of gas bubbles ; under these condi- 

 tions, whitish cloudy flocculi are found in the whey, which 

 are full of spores. 



id) The spores do not lose their power to germinate if 

 exposed to 80° C. for fiftee'n minutes ; they are, however, 

 killed if immersed in boihng water for two minutes. 



{e) The cultures in gelatine, as also in milk, have a distinct 

 smell of butyric acid, this is more pronounced the older the 

 culture. 



Cultures in sugar gelatine, as also cultures in milk, while 

 young, not more than a week old, when injected into the 

 subcutaneous tissue of guinea-pigs or mice prove virulent. 

 Half to three-quarters of a cubic centimetre of the Hquefied 

 gelatine culture, or of the whey of a milk-culture, per 200 

 grammes body-weight of guinea-pig, injected under the skin 

 of the groin, causes distinct illness already in six to eight 

 hours : the animals are quiet, do not feed, they have 

 oedematous swelling about the seat of injection, and the 

 body temperature is lower than normal ; their muscular 

 movements become gradually greatly impaired, and they are 

 found dead between twenty and twenty-four hours. Smaller 

 quantities produce the fatal result in two, or even three 

 days, and very small quantities cause only temporary illness 

 and transitory local sweUing. 



On post-mortem examination, the subcutaneous and 

 muscular tissue of the groin, of the whole of the abdomen 



