252 INFECTIVE DISEASES. 



by the end of five or six days it consisted of an elevated mass, doughy 

 to the touch, almost circular, with a diameter of six inches. The 

 skin over the swelling was livid and dimpled. The swelling was in 

 some cases due to purulent effusion, but more frequently on incision 

 there was only an escape of sero-sanguineous fluid. The cervical 

 glands in very severe cases sometimes attained an enormous size. 



Three out of seven Japanese medical men were attacked and one 

 died, but none out of eleven English doctors, though they were equally 

 exposed to infection. Of eight Englishmen attacked seven were among 

 the soldiers employed, and only two died. No nurses or attendants 

 on the sick were attacked. The virus appeared to be intimately 

 connected with filth in the soil. According to the Chinese, rats, 

 poultry, goats, sheep, cows, and buffaloes are susceptible. In the 

 houses and hotels dead rats were found in great numbers : it was said 

 that they emerged from their haunts in sewers and drains, appeared 

 to be dazed, and limped about, owing to the formation of buboes in 

 their hind legs. Rats, mice, and guinea-pigs inoculated with virus 

 from a human lymphatic gland died with development of buboes. 

 It appears to be clearly proved that rats suffer from the plague in 

 common with man, and it has also been suggested that they may 

 serve to spread the disease. Bacilli were found in human blood and 

 in the swollen lymphatic glands by Kitasato, and independently by 

 Yersin. 



Bacillus of Plague. Short rods with rounded ends. They 

 stain with aniline dyes, but not by Gram's method. The stain 

 collects at the ends of the rods, leaving a clear space in the middle. 

 Sometimes the rods are surrounded by a capsule. They are found 

 in abundance in the buboes, and in small numbers in the blood in 

 very serious and rapidly fatal cases. 



Material from the buboes inoculated on agar gives rise to white 

 transparent colonies, which have an iridescent edge when examined 

 by reflected light. 



The bacilli grow more readily on glycerine-agar and on solidified 

 serum. In broth cultures the liquid remains clear, and a flocculent 

 deposit forms on the sides and at the bottom of the vessel. 



An alkaline solution of peptone 2 per cent., with from 1 to 2 per 

 cent, of gelatine, is the best nutrient medium. In cultures the 

 bacilli develop chains of short rods and well-marked involution 

 forms. Swollen and degenerated forms are found most abundantly 

 in old cultures, and stain with difficulty. 



Mice, rats, and guinea-pigs, inoculated with bubonic tissue, die in 

 a few days, numerous bacilli being found in the lymphatic glands. 



