it is not impossible
for such modified virus to regain its original virulence after it has been
scattered broadcast by the inoculation of large herds. It is obviously
unsafe to have such vaccine injected by a layman; instead, it should be
handled only by a competent veterinarian.

There are other disadvantages in this method of vaccination, and they all
must be given due consideration. The unstable keeping quality of the
Pasteur vaccine is a very important factor to be considered. Experience in
this line has proved that Pasteur vaccine may deteriorate within a very
short time after its preparation, and in repeated instances it has proved
inert within three months of its preparation. When exposed to warm
temperature and light, it deteriorates very rapidly; and when it is
considered that the products of manufacturers may be stored under
unfavorable conditions in branch houses and on the shelves of rural drug
stores, the loss of potency can be readily explained. These deficiencies
have been recognized by many investigators, and because of the superior
keeping qualities particular attention has been directed toward the
preparation of a spore vaccine by Zenkowsky of Russia, Detre of Hungary,
and Nitta of Japan. For the purpose of producing a spore vaccine it is
desirable to use a peptone-free agar medium, and after inoculation with an
attenuated culture of the anthrax bacillus, it is allowed to grow at a
temperature of 37 deg. C. for 4 to 7 days. By this time an abundance of spores
will have formed. The growth is then collected in sterile flasks and heated
to a temperature of 60 deg. C. for one-half hour to destroy the vegetative
forms of the organism. If it is desired to use for vaccination one million
spores, it is advisable to dilute the vaccine to a quantity of which 1
cubic centimeter would contain this number. Of such a vaccine 1 cubic
centimeter would constitute the dose for cattle and horses. In all forms of
vaccination against anthrax in sheep the greatest care must be exercised,
as these animals are very susceptible to the disease, and at times vaccines
which have no ill effects on cattle will prove fatal to sheep. Therefore
the dose of the spore vaccine for sheep should not be more than one-fourth
of that given to cattle.

Sclavo, Sobernheim, and others have established that injections of
increasing quantities of virulent cultures into immune animals produced a
serum which has great protective value against anthr