MICROCOCCUS TETRAGENUS. 245 



by inoculating the same culture into rabbits in varying 

 amounts. 



Rabbits, mice, guinea-pigs, dogs, rats, cats, and sheep 

 are susceptible to infection by this organism. Chickens 

 and pigeons are insusceptible. Young animals, as a 

 rule, are more easily infected than old ones. Rabbits 

 and mice are the most susceptible of the animals used 

 for experimental purposes, and in testing the virulence 

 of a culture it is well to inoculate one of each, for with 

 the same cultures it sometimes occurs that it may be 

 virulent for mice and not for rabbits, and vice versa. 



If the culture is virulent, intra-vascular or intra- 

 peritoneal injections into rabbits may produce rapid 

 and fatal septicaemia, while subcutaneous inoculation of 

 the same material may result in only a localized in- 

 flammatory process. On the other hand, subcutaneous 

 inoculation of less virulent cultures may produce a local 

 process, while intra-venous inoculation may be without 

 result. This organism is the cause of a number of 

 pathological conditions in human beings that have not 

 hitherto been considered as related to one another etio- 

 logically. It is always present in the inflamed area of 

 the lung in acute fibrinous or lobar pneumonia ; it is 

 known to cause acute cerebro-spinal meningitis, endo- 

 and pericarditis, certain forms of pleuritis, arthritis 

 and peri- arthritis, and otitis media. 



b. SEPTICEMIA CAUSED BY THE MICROCOCCUS 

 TETEAGENUS. 



Should the death of the animal not occur within the 

 first twenty-eight to thirty hours after inoculation, but 

 be postponed until between the fourth and the eighth 



