540 PATHOGENIC AEROBIC BACILLI 
white color and cream-like consistence. The growth upon potato varies at 
different times, evidently owing to ditferences in the potato. 
When stained preparations are examined with the full light of the Abbe 
condenser the ends of some of the rods appear to be cut away, leaving a con- 
cave extremity; but by using a small diaphragm to obtain definition it will 
be seen that the cell wall extends beyond the stained portion of the rod and 
includes what appears to bea vacuole. There is no reason to believe that 
this appearance is due to the presence of an end spore, for the supposed 
vacuole is not refractive, as a spore would be, and my experiments on the 
thermal death-point of this bacillus indicate that it does not form spores. 
Cultures are sterilized by exposure for ten minutes to a temperature of 160° 
F. (71.2° C.). 
Pathogenesis.—Very pathogenic for rabbits when injected into the cavity 
of the abdomen. Injections of asmall quantity of a pure culture into the 
ear vein or subcutaneously generally give a negative result. Injections of 
from one to five cubic centimetres of a culture in bouillon, blood serum, or 
agua coco, into the cavity of the abdomen, frequently prove fatal to rabbits 
in a few hours—two to six. 
The negative results obtained in injecting cultures beneath the skin or 
into the ear vein of rabbits show that this bacillus does not induce a fatal 
septicemia in these animals, and the fatal result when injections are made 
into the peritoneal cavity does not appear to be due to an invasion of the 
blood, but rather to the local effect upon the peritoneum, together with the 
toxic action of the chemical products resulting from its growth. 
It is true that I have always been able to recover the bacillus from the 
liver, or from blood obtained from one of the cavities of the heart, even in 
animals which succumb within a few hours to an injection made into the 
cavity of the abdomen. But the direct examination of the blood shows that 
the bacilli are present in very small numbers, and leads me to believe that 
the bacillus does not multiply, to any considerable extent at least, in the 
circulating fluid. 
The spleen is not enlarged, as is the case in anthrax, rabbit septicemia, 
and other diseases in which the pathogenic microdrganism multiplies abun- 
dantly in the blood. 
On the other hand, there is evidence of local inflammation in the peri- 
toneal cavity. When death occurs within a few hours the peritoneum is: 
more or less hyperzemic and there is a considerable quantity of straw-colored. 
fluid in the cavity of the abdomen. When the animal lives for twenty 
hours or more there is a decided peritonitis with a fibrinous exudation upon 
the surface of the liver and intestine. Usually the liver, in animals which: 
die within twenty-four hours, is full of blood, rather soft, and dark in color. 
ae a single instance I found the liver to be of a light color and loaded with 
at. 
The rapidly fatal effect in those cases in which I have injected two or 
more cubic centimetres of a culture into the cavity of the abdomen has led 
me to suppose that death results from the toxic effects of a ptomaine con- 
tained in the culture at the time of injection. The symptoms also give sup- 
port to this supposition. The animal quickly becomes feeble and indisposed 
to move, and some time before death lies helpless upon its side, breathing 
regularly, but is too feeble to get up on its feet when disturbed. Death some- 
times occurs in convulsions, but more frequently without—apparently from 
heart failure. 
Pathogenic also for guinea-pigs when injected into the cavity of the 
abdomen, but death does not occur in so short a time—eighteen to twenty 
hours. The comparative researches of Reed and Carroll indicate that this is: 
a pathogenic variety of the colon bacillus. 
