DISTRIBUTION OF THE BACILLI. 



439 



oxgyen ; in strictly anaerobic conditions almost no growth takes 

 place. 



The organism in its powers of resistance corresponds with 

 other spore-free bacilli, and is readily killed by heat, an exposure 

 for an hour at 58 C. being fatal. On the other hand, it has 

 remarkable powers of resistance against cold ; it has been ex- 

 posed to a temperature several degrees below freezing-point 

 without being killed. Experiments on the effects of drying 

 have given somewhat diverse results, but as a rule the organism 

 has been found to be dead after being dried for from six to eight 

 days, though sometimes it has survived the process for a longer 

 period ; exposure to direct sunlight for three or four hours 

 kills it. When 

 cultivated out- 

 side the body 

 the organism 

 often loses its 

 virulence, but 

 some races re- 

 main virulent 

 in culture for 

 a long period 

 of time. 



Anatomical 

 Changes and 

 Distribution of 

 Bacilli. The 

 disease occurs 

 in several 

 forms, the bu- 

 bonic and the 



FIG. 151. Section of a human lymphatic gland in plague, 

 showing the injection of the lymph paths and sinuses with masses 



pulmonary be- ^ P la S ue bacilli seen as black areas. 



Stained with carbol-thionin-blue. X 50. 



ing the best 



recognised ; to these may be added the septiccemic. The most 

 striking feature in the bubonic form is the affection of the 

 lymphatic glands, which undergo intense inflammatory swell- 

 ing, attended with haemorrhage, and generally ending in a 

 greater or less degree of necrotic softening if the patient lives 

 long enough. The connective tissue around the glands is 

 similarly affected. The bubo is thus usually formed by a col- 



