Distribution in Nature 543 



Distribution in Nature. — ^The spirochseta of rat-bite fever seems 

 to be a pathogenic parasite of rats. It, like other parasites is not 

 present in all rats, but only in those suffering from or convales- 

 cent from infection, and seems to be spread from animal to animal 

 through bites. In no case has the spirochseta been found in healthy 

 guinea-pigs or mice, yet guinea-pigs readily contract the infection 

 when bitten by a diseased rat, and men when bitten sometimes 

 do the same. The spirochseta is not found in the saliva of the rat 

 and probably accidentally enters it through admixture of blood from 

 the gums. 



Pathogenesis. — The organisms are pathogenic for rats, white- 

 rats, mice, guinea-pigs, monkeys and man, but not for rabbits. 



Distribution in the Animal Body .—Klw&ys present in the blood of 

 mfected animals, though not always in numbers permitting dis- 

 covery by direct observation, they pervade the body but collect 

 chiefly in the liver and kidneys. 



Lesions. — In general the lesions consist of swelling and congestion 

 of the lymph nodes, congestion of the liver and lungs, congestion, 

 swelling and sub-capsular as well as interstitial hemorrhages in the 

 kidneys, congestion and hemorrhage of the adrenals. 



Treatment. — The spirochaetae quickly disappear from the blood 

 of guinea-pigs when salvarsan is administered, in which particular 

 they differ from those of infective jaundice which were much less 

 susceptible to the effects of the arsenic compounds. 



