550 PATHOGENIC AEROBIC BACILLI 
dirty-white, moist layer. The cultures in media containing albumin 
or gelatin have a putrefactive odor and acquire a strongly alkaline 
reaction. A temperature of 20° to 24° C. is most favorable for the 
growth of this bacillus. It isa facultative anaérobie and grows in 
an atmosphere of hydrogen or of carbon dioxide, although not so 
rapidly as in the presence of oxygen. The movements are often ex- 
tremely active and difficult to follow under the microscope ; again 
they may be quite deliberate, or the bacilli may remain motionless 
for a time and again dart off in active motion. The long terminal 
flagella may sometimes be discerned by means of a good objective 
and careful manipulation of the light. 
Pathogenesis.—Pathogenic for rabbits and for guinea-pigs when 
injected into the circulation, into the cavity of the abdomen, or sub- 
cutaneously in considerable quantity. Cultures in nutrient gelatin 
are said by Cheyne to be more pathogenic (toxic) than those in bouil- 
lon. When injected into the muscles of rabbits a much smaller 
dose produces a fatal result than when injected subcutaneously. 
In Cheyne’s experiments, made in London (1886), one-tenth cubic 
centimetre of a liquefied gelatin culture, injected into the dorsal 
muscles, was invariably fatal in from twenty-four to thirty-six hours; 
a dose of one-twentieth cubic centimetre, injected in the same way, 
usually caused death; while one-fortieth cubic centimetre gave rise to 
an extensive local abscess, and the animals died at the end of six or 
eight weeks. Dosesof less than one-five-hundredth cubic centimetre 
produced no effect. Cheyne estimates that one cubic centimetre ofa 
culture in nutrient gelatin contains 4,500,000,000 bacilli, and, conse- 
quently, that a smaller number than 9,000,000 produced no effect when 
injected into the muscular tissue of rabbits. Injections into the sub- 
cutaneous connective tissues of a dose twice as large as that which in- 
variably proved fatal when injected into the muscles usually caused 
an extensive abscess, but did not kill the animal; and, after re- 
covery from the effects of such an injection, the rabbit was found to 
be immune against a similar dose injected into the muscles. Foa 
and Bonome have succeeded in producing immunity against the 
etrects of virulent cultures of this bacillus by inoculating rabbits with 
filtered cultures, and also by injecting beneath the skin of these ani- 
mals a solution of neurin, which they believe to be the principal 
toxic product present in the cultures. 
Proteus Vulgaris in Cholera Infantum.—The extended re- 
searches of Booker have led him to the conclusion that this bacillus 
plays an important part in the production of the morbid symptoms 
which characterize cholera infantum. Proteus vulgaris was found 
in the alvine discharges in a considerable proportion of the cases ex- 
amined, but was not found in the feeces of healthy infants. ‘‘ The 
