224 3Ianual of Veterinary Microbiology. 



form of a homogeneous rod, or more frequently com- 

 posed of granules arranged in linear series. It is 

 straight or bent in the form of an arc, sometimes 

 S-shaped; it measures 2/^ to 6/i in length by 0-3/i to 

 0-5;^ in thickness. The rod is uniform in size through- 

 out its extent. 



According to Cornil and Bab^s the granular appear- 

 ance is especially observed in bacilli long abandoned 

 to the air ; these authors have demonstrated the same 

 granules in bacilli coming from cultures and they re- 

 gard them as spores. 



A certain number of the bacilli are 

 observed to become considerably elon- 

 gated and to swell at one of their ex- 

 tremities; we have often seen these 

 abnormal forms in bouillon cultures 

 of avian tuberculosis. 



Action of -physical and chemical agents. — Tubercle 

 bacilli are killed by a temperature of 70°, maintained 

 during ten minutes (Yersin). According to M. Gal- 

 tier, heating at 71° during ten minutes does not suffice 

 to sterilize tuberculous matter. Moist heat at 100° 

 sterilizes it with certainty in a few minutes, but this 

 is not the case when the virulent substance is in the 

 dry state, for the dried spores withstand 100°. 



The tubercle bacillus withstands freezing, putrefac- 

 tion and desiccation. This last operation, when it 

 occurs at temperatures near to 30°, is, indeed, an im- 

 portant means of preserving it. The bacillus retains 

 its vitality for a considerable time in sterilized water 

 (seventy days). 



According to Yersin, carbolic acid, at 5 per cent, 

 kills the bacillus in half a minute ; sublimate, at 1 to 



