, is mixed with
definite quantities of sterile water, filtered, and by means of a
hypodermic syringe the filtrate injected under the skin in front of the
shoulder of the animal. The inoculation is usually followed by
insignificant symptoms. In a few cases there is a slight rise of
temperature, and by close observation a minute swelling may be noted at the
point of inoculation. The immunity conferred in this way may last for 18
months, but animals vaccinated before they are 6 months old and those in
badly infected districts should be revaccinated before the following
blackleg season.

The effect of the vaccine prepared by this bureau in preventing outbreaks
of the disease and in immediately abating outbreaks already in progress was
highly satisfactory, and it is not to be doubted that thousands of young
cattle were saved to the stock owners during the 25 years in which the
vaccine was distributed.[6] More than 47,000,000 doses were sent out during
this period, and from reports received it is safe to conclude that more
than 40,000,000 were actually injected, whereby the percentage of loss from
blackleg has been reduced from 10 per cent, which annually occurred before
using, to less than one-half of 1 per cent per annum. With these figures
before us it is plain that the general introduction of preventive
vaccination must be of material benefit to the cattle raisers in the
infected districts. Moreover, there is every reason to believe that with
the continued use of blackleg vaccine in all districts where the disease is
known to occur, and an earnest effort on the part of the stock owners to
prevent the reinfection of their pastures by following the directions
given, blackleg may be kept in check and gradually eradicated.

Immunization against blackleg is now frequently accomplished by the use of
the so-called blackleg aggressin and blackleg filtrates.

NECROTIC STOMATITIS (CALF DIPHTHERIA).

[Pl. XLIII.]

Necrotic stomatitis is an acute, specific, highly contagious inflammation
of the mouth occurring in young cattle, and characterized locally by the
formation of ulcers and caseo-necrotic patches and by constitutional
symptoms, chiefly toxic.

This disease has also been termed calf diphtheria, gangrenous stomatitis,
ulcerative stomatitis, malignant stomatitis, tubercular stomatitis, and
diphtheritic patches of the oral mucous membrane.

_History._--During the last few years farmers and cattlemen in this
country, es