294 YELLOW FEVER; BUBONIC PLAGUE; INFLUENZA. 



Infection : The plague bacillus usually gains entrance to 

 the body through slight injuries of the skin, although the 

 organism may be inhaled and lodge in the lung. The injury 

 of the skin may be imperceptible and the infection atria may 

 be very numerous. Insect-bites may be the source of infec- 

 tion. At the site of infection a localized suppuration devel- 

 ops, which spreads along the lymphatics to the nearest chain 

 of glands. These glands swell up, and finally suppurate and 

 form buboes, from which the disease has its name of bubonic 

 plague. 



In mild cases the infection does not spread further ; but 

 in severe cases the lymph-glands in remote parts of the body 

 are also affected. The bacilli may finally make their way into 

 the blood-current, and from there to all parts of the body. 



When infection occurs through the respiratory tract, a 

 typical pneumonia is produced. The plague bacilli are found 

 in the sputum, and may be associated with the streptococcus 

 and diplococcus. Tonsillar infection has also been observed. 

 When infection occurs in that way, the disease is rapidly 

 fatal. 



Prophylaxis : In the prophylaxis of plague general hygienic 

 precautions are of first importance : Properly ventilated 

 dwellings ; personal cleanliness ; prompt surgical care of any 

 wounds or insect-bites ; the careful avoidance of anything 

 suggestive of filth ; the immediate disposition of all dead 

 rats, especially in plague-infected localities ; and the destruc- 

 tion of as many live rats as possible. The patient should be 

 isolated and watched, so that the infection does not spread to 

 the attendants or members of the family. The bodies of 

 persons dead of plague should be disposed of very promptly 

 after thorough disinfection. Cremation is the best and most 

 thorough method of disposition. 



Immunization : Susceptible animals can be immunized with 

 dead cultures of the plague bacillus. Haffkine's protective 

 inoculation against plague consists of the injection of 0.5 to 

 2.5 c.c. of a devitalized culture of the plague bacillus. The 

 injection is repeated after eight or ten days. Yersin immu- 

 nizes animals by the intravenous or intraperitoneal injection 

 of dead cultures or by repeated subcutaneous inoculation. 



