The Microscope. 131 



marked rarefaction of the cultivating medium. In studying the 

 influence of temperature and dryness on the cultures, it was found 

 that the micrococcus develops in two distinct forms : a transitory and 

 a more permanent. 



Inoculation experiments were made on dogs, rabbits, guinea- 

 pigs, mice, and birds. With the exception of the last, which suc- 

 cumbed to what seemed to be blood poisoning, all the animals pre- 

 sented only one form of pathological manifestations, which was most 

 clearly seen in the rabbits and guinea-pigs. Of a total of eighty 

 animals experimented upon, only four were refractory and escaped 

 fatal consequences fi'om the inoculations. The micrococcus possesses 

 very pronounced infectious power, which seems to be chiefly exerted 

 upon the respiratory apparatus. This virulence is endowed with a 

 capacity of resistance which is remarkable, persisting in the cultures 

 for several months, and resisting successive passages through the 

 animal organism, as was shown by series of inoculations on the 

 animals. It resists desiccation to a marked degree. 



As a rule the animals died from the seventh to the twelfth day. 

 At the autopsy there was enormous tumefaction of the parenchy- 

 matous organs, principally of the spleen and lymphatic ganglia. 

 The tumefied organs were studded with gray or grayish-yellow 

 nodules. Independently of the nodules the lungs contained the 

 characteristic lesions of a more or less extensive pneumonia, even in 

 the stage of hepatization, even when the inoculation was made in the 

 subcutaneous cellular tissue. The nodules belonged to the class of 

 granuloma, or infectious tumors with granulations. They usually 

 go on to calcification, which begins at the center; they contain the 

 specific micrococci, and are infectious. 



This new micrococcus usually leads an intracellular existence, 

 and its pathogenic action consists in provoking caseous necrosis of 

 the parenchyma of the cellule. More rarely they are found outside 

 the cellular elements, and very exceptionally in the vessels. In the 

 foci of degeneration and necrosis developed about it this micrococcus 

 is not killed, for it can exist in a state of great rarefaction or dilu- 

 tion of the elements necessary for its existence. 



The pathogenic action of this schizomycete is exerted principally 

 on the lymphatic system, which represents at the same time both 

 the port of entry of the infection and the most favorable medium for 

 the development of the infectious agent. AYhen the latter is inocu- 

 lated into the subcutaneous cellular tissue there is formed, at the 

 seat of the inoculation, a nodule which often grows very large, and 

 which is made up of a plastic exudate on the way to caseation. It 



