FRIEDLANDER'S BACILLUS 147 



and dogs less so. Rats seem to be affected with a chronic form of the 

 malady, and by inhabiting ships and warehouses in foreign countries, 

 spread the disease. Post mortems on infected animals reveal haemor- 

 rhagic petechia and serous infiltration into serous cavities. Death 

 is generally due to a profound toxaemia and exhaustion. 



The virulence of the organism can be raised by passing it through 

 a series of animals. 



Serum from infected animals agglutinates plague bacilli. 



The diagnosis of the plague bacilli is made by rubbing the sus- 

 pected culture upon the freshly shaven skin of a guinea pig; if the 

 animal developes buboes and dies, and polar staining bacilli are 

 found, it is probable that the organism is the plague bacillus. Fur- 

 ther, if curious involution forms develop on heavily salted agar 

 (3 percent) the diagnosis is confirmed. (Fig. 47.) 



The disease is spread by flies which, according to Yersin, are 

 susceptible to the disease, and spread it by depositing their feces 

 on the human skin, rather than through their bites. 



Immunity. It is possible to immunize against the disease. 

 Kitasato and Yersin produced an anti-toxic serum, which has, not 

 only a prophylactic, but a curative action. By the use of killed 

 culture Haffkine vaccinated many people against the plague very 

 successfully. 



FRIEDLANDER'S BACILLUS. 



Bacterium Pneumoniae. 



Friedlander' s Pneumonia Bacillus. (Fig. 48.) 



Morphology and Stains. Short plump rods with rounded ends, 

 surrounded by a thick gelatinous capsule in animal fluids, and when 

 grown in milk; is not motile, and has no spores; does not stain by 

 Gram's method, but easily by the common basic dyes. 



Oxygen Requirements. Grows in and without oxygen, upon 

 all culture media. 



Chemical Activities. Produces abundant acids, CO 2 and H. 

 gas, alcohol, indol, ferment and H 2 S. 



