406 BACILLUS AEROGENES CAPSULATUS. 



dering into the circulation from the intestine just before, or 

 immediately after, death. 



Isolation and Identification. The suspected material should 

 be transferred in varying quantities to milk and incubated under 

 anaerobic conditions for forty-eight to seventy-two hours, when 

 the typical reaction should be manifest. An incomplete reac- 

 tion may be brought about by the partial overgrowth of other 

 bacteria, but usually upon sub-culture in the same medium it 

 will obtain a sufficient start to bring about the typical change. 

 To finally obtain the bacillus in purity, and at the same time to 

 have a positive means of identification, Professor Welch has 

 devised a very ingenious method : From |-i c.c. of such a milk 

 culture, or the same quantity of a suspension made from a solid 

 medium, is injected into the ear vein of a rabbit, and to insure a 

 thorough distribution of the organisms three minutes are allowed 

 to pass before the next step is taken, which is the killing of the 

 animal by a sharp blow on the back of the head. The body is 

 now placed in the thermostat for seven or eight hours, or left at 

 room temperature for eighteen or twenty-four hours, and at the 

 end of either of those periods the animal will usually be found 

 to be greatly bloated, due to accumulation of gas in the subcu- 

 taneous tissue and in the body cavities. As the gas is highly 

 inflammable a lighted match brought to a puncture in the ab- 

 dominal wall, or elsewhere, will produce a bright blue flame 

 when in contact with the escaping gas. The organs of the 

 animal will be found to be full of gas and more or less broken 

 down. The organism is then found in enormous numbers every- 

 where and readily identified by its capsule, absence of motility, 

 staining by Gram, and later, if some serum from the animal is 

 sealed up in a small tube and placed in the thermostat it will be 

 found that many of the bacilli have formed spores. This latter 

 fact was pointed out by E. Klein in his studies on his B. enteri- 

 tidis sporogenes (B. aerogenes capsulatus). 



