404 BACILLUS AEROGENES CAPSULATUS. 



markedly emphysematous ; it is notable that in these cases no 

 gas was found in the blood during abstraction of it with the 

 syringe, although closely watched for. 



In the lower animals, infections by this bacillus have been 

 rarely met with under natural conditions. Harris, however, has 

 observed local abscesses in the dog and rabbit following upon 

 simple surgical procedures. Under artificial conditions B. aerog- 

 enes capsulatus is pathogenic for the guinea-pig and pigeon, 

 but practically not for the rabbit and mouse. Experience has 

 shown that the virulence of the bacillus towards guinea-pigs, 

 when injected subcutaneously, varies exceedingly. Certain races 

 are absolutely harmless ; some produce local swelling, with or 

 without necrosis and ulceration, whilst others will produce death, 

 accompanied by subcutaneous emphysema and a peculiar diges- 

 tive-like action upon the subcutaneous tissues and abdominal 

 muscles, so that the intestines can plainly be seen lying in the 

 cavity. There is also much bloody serous fluid along with this 

 necrotic process. 



Cultural Characters. The bacillus is an obligate anaerobe. 

 The surface colonies on plain-agar plates appear to the unaided 

 eyes to be well circumscribed, round, flat, grey-white, translu- 

 cent, smooth, and glossy, with a diameter varying from 1.5 to 4 

 mm. The deep colonies are seen as small white points, some- 

 times indistinctly limited. Under the low power of the microscope 

 the surface colonies are found to be not infrequently irregular, 

 with a central mass or nucleus embedded in a surrounding finely 

 granular growth of a light brown-yellow colour, whose periphery 

 is regular and often delicately fringed. The deep colonies are 

 usually of a clear-cut oval or round shape, but occasionally they 

 appear to be surrounded with woolly outgrowths, similar in 

 character to those of B. tetani. On agar slants the surface 

 growth is thin, grey, translucent, glossy, and veil-like; at times 

 difficult to detect. 



In shake-cultures, especially in glucose agar or ghtcose gelatin, 

 gas formation is very profuse, so that the medium becomes split 

 up into layers, the uppermost often pressing against the cotton 

 plug. There is an accompanying heavy peculiar odour lacking 

 putrefactive taint. Upon potato the growth is usually scant, 

 invisible, or quite negative. Occasionally, however, it is well 

 marked, of a yellow-white colour, semi-lustrous, moist, and show- 



