326 BACTERIOLOGY. 



conditions may sometimes be produced by inoculating 

 rabbits with the same cultures 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 the 

 same culture may sometimes be virulent for mice and 

 not for rabbits, and vice versa. 



If the culture is virulent, intravascular 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 inflamma- 

 tory process. On the other hand, subcutaneous inocula- 

 tion of less virulent cultures may produce a local process, 

 while intravenous 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 etiologically. 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 peri -carditis, 

 certain forms of pleuritis, arthritis and peri-arthritis, 

 and otitis media. 



b. SEPTICEMIA CAUSED BY MICEOCOCCUS TETRAGENUS. 



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 eighth day, it 

 may result from the invasion of the tissues by the organ- 

 ism now to be described, viz., micrococcus tetragenus. 



