124 THE ACUTE SELF-LIMITED INFECTIONS 



For diagnosticating this disease an abscess is punc- 

 tured, the pus withdrawn, and slide smears and cultures 

 are made. The bacilli are found in countless numbers. 

 Cultivation on ordinary media is simple. A blood 

 culture will also reveal their presence. At death 

 bacteria will be found in practically every organ in 

 the body. 



The plague bacillus is a short plump rod, TT~O"O~O to 

 -nrfor inch long by ^imnr to -girihro inch wide. It does 

 not move nor form spores. It grows best at 35 C. 

 or 92 F. It is stained with reasonable ease, displaying 

 a peculiar picture. The bacilli are short thick rods 

 with rounded ends. The end sections stain much 

 more densely than the middle part, called bipolar 

 staining. These rods may grow longer and appear 

 in pairs or short chains. They are killed by 60 C. 

 or 142 F. in ten minutes, or by boiling water in two 

 minutes. They resist drying for two or three days 

 under natural conditions, but when drying is hastened 

 by artificial means, they live only a few hours. They 

 resist cold and freezing for a long time, perhaps a 

 month. Sunlight destroys them in five hours. In 

 pus or sputum they may live a few weeks, but in 

 cadavers they have been found after several months. 

 Chemicals kill them as follows: 5 per cent, carbolic 

 acid and 1 to 1000 bichloride in ten minutes. Animals 

 are usually susceptible to Bacillus pestis, particularly 

 guinea-pigs and rats, and it is said that simple rubbing 

 of them on the skin of these beasts will produce the 

 infection. It is similar to the human disease. 



Plague Serum. The poison of Bacillus pestis is 

 largely intracellular. It has been possible, however, 



