pecially in Colorado, Texas, and South Dakota, have increasingly
noted the occurrence of enzootics of "sore mouth" among the young animals
of their herds. Instead of healing, like the usual forms, of themselves,
these cases, if untreated, die. Careful study of some of them has resulted
in their identification with cases reported in 1877 by Dammann, from the
shore of the Baltic; in 1878 by Blazekowic, in Slavonia; in 1879 by
Vollers, in Holstein; in 1880 by Lenglen, in France; in 1881 by
Macgillivray, in England; and in 1884 by Loeffler, who isolated and
described the microorganism which produces the disease. Bang obtained this
organism from the diphtheritic lesions of calves in 1890, and Kitt likewise
recovered the bacillus from similar lesions of the larynx and pharynx of
calves and pigs in 1893.

[Illustration: PLATE XLII. SECTION OF MUSCLE FROM A BLACKLEG SWELLING.
a. GAS BUBBLES.
b. CAVITIES DUE TO GAS FORMATION.]

[Illustration: PLATE XLIII. NECROTIC STOMATITIS (CALF DIPTHERIA).]

_Etiology._--The cause of necrotic stomatitis, as demonstrated by Loeffler
and since confirmed by other investigators, is _Bacillus necrophorus_,
often spoken of as the bacillus of necrosis. This organism varies in form
from a coccoid rod to long, wavy filaments, which may reach a length of
100 mu; the width varies from 0.75 mu to 1 mu. Hence it is described as
polymorphic. It does not stain by Gram, but takes the ordinary anilin dyes,
often presenting, especially the longer forms, a beaded appearance. A
characteristic of the organism, of great moment when we come to treatment,
is that it grows only in the absence of oxygen, from which fact it is
described as an obligate anaerobe.

Very few organisms exhibit a wider range of pathogenesis. According to
clinical observation to the present time, _Bacillus necrophorus_ is
pathogenic for cattle, horses, hogs, sheep, reindeer, kangaroos, antelope,
and rabbits. Experimentally it has been proved pathogenic for rabbits and
white mice. The dog, cat, guinea pig, pigeon, and chicken appear to be
absolutely immune. It is not pathogenic for man.

The importance of this bacillus is far beyond even its relation to necrotic
stomatitis. Besides this disease it has been demonstrated as the causative
factor in foot rot, multiple liver abscesses, disseminated liver necrosis,
embolic necrosis of the lungs, necrosis of the heart, in cattle; gangrenous
pox of the teats, diphtheria of the uterus