IQ2 ESSENTIALS OF BACTERIOLOGY 



man. Infected ground squirrels are supposed to be a factor 

 in spreading the disease. Animals protected from the flea 

 may live near infected animals without danger. Direct in- 

 fection by dust or other material seldom occurs. The sputum 

 of patients having the pneumonic type is highly infectious. 

 Close personal contact with the infected is a means of trans- 

 mission. The main point of entrance is the skin. Fifty per 

 cent, of wild rats immune and not easily affected. 



Products. A toxin has been obtained and immunity has 

 been effected; the serum of immune animals has protective 

 properties. The serum likewise shows agglutinating powers, 

 and gives similar reactions to typhoid and cholera sera. 



Habitat. Not found in water, but most likely spreads from 

 the soil in damp and darkened areas. Rats become affected 

 first, and then, through fleas, affect man and other animals. 

 In man three forms of the disease are recognized according to 

 the mode of infection and course of the disease viz., bubonic, 

 pulmonic, septicemic. 



Vaccines. The vaccines of Haffkine and Terni and Bandi 

 have been used extensively, and with some good results. 



Antitoxins. The antitoxins of Yersin and of Lustig have 

 been used, but without much result. Closely identified with 

 Bacillus pestis is the group known as the hemorrhagic sep- 

 ticemia bacteria 



Bacteria of Hemorrhagic Septicemia (Hueppe, 1886). 

 Under this heading Hueppe has gathered a number of 

 bacteria very similar to the bacillus of chicken cholera, differ- 

 ing from it and each other but very little. They have been 

 described by various observers and found in different diseases. 



The bacteria of this group color themselves strongly at the 

 poles, giving rise to the dumb-bell shape (Fig. 97). They 

 do not take the Gram stain; they are without spores, and do 

 not liquefy gelatin. 



They have been divided into three groups, Bacillus avi- 

 septicus, as it appears in fowls; Bacillus bovisepticus, as it 

 attacks cattle; Bacillus suisepticus, as it attacks swine. 

 The prominent members of each group are: Bacillus of 



