12
out buildings of the Laboratory were practically completed, and four salted
animals, which had recovered from an attack of the disease at the time of the
experiments made when Professor Koch visited the Laboratory 18 months
before, were available for the purpose, and were inoculated with increasing
doses of virulent blood until 1,000 c.c. were given at once, and were then
bled for the production of serum and reinoculated again with still larger doses,
in accordance with the details described by Turner and Kolle. Subsequently,
some of the serum obtained from one of these was used for passing six more
animals through a mild attack of the disease, and these too were then inocu-
lated in the same way as the first series and serum obtained from them, so that
at the present date some 30,000 c.c. of serum have been made. When a
centrifugal machine, which has been ordered, reaches the Laboratory, more than
twice as much serum will be able to be prepared from the same quantity of
blood as is at present possible. It is worthy of note that in all our first bleed-
ings only from 11 to 15 per cent. of serum was obtained from the blood taken,
which was very disappointing. As it seemed probable that the quantity that
separates from the clotted blood would depend on the firmness of the clot
itself more than on any other factor, and as, moreover, it is known that the
clotting power of the blood can be very materially increased by the adminis-
tration of Calcium Chloride, it was determined to administer this drug before
bleeding the animals. The result was most satisfactory, as in this way from
30 to 40 per cent. of serum was obtained, and the great difference between
the quantity obtained from animals with and without the use of the drug was
repeatedly verified, as different animals were found to give different quantities
of serum. Moreover, it was found that a greater quantity of serum was
obtained by the use of two doses, each of half an ounce, one given the evening
before and the other on the same morning as the bleeding but some three
hours before, than by a single dose given on the same morning as the blood
was taken. All our animals are now treated in this way, and there is no
evidence to show that the quality of the serum is in any way affected by the
drug, while, if anything, it might be expected to lessen the uticaria which some-
times follows the injections of the serum.
One other point of practical importance, which has been worked out in the
course of these experiments on making serum, may be mentioned here. The
main difficulty in carrying it out is that of obtaining of large quantities of
virulent blood, for which purpose control animals have to be inoculated and sub-
sequently bled when the disease has fully developed. As, for the sake of economy,
the small Hill cattle are used for this purpose, it was found that only some
2,000 c.c. of blood could be obtained from the jugular vein of an animal
before heart failure set in, the flow ceased, and the animal shortly after died.
On the other hand, by bleeding from the carotid artery, only 3,000 c.c. were
obtained, but the process was a peculiarly repulsive one, convulsions being
caused. In South Africa very much larger animals are used, and although
they are bled to death a very much larger quantity of blood is obtained from
one animal, and the process does not require to be repeated nearly so often as
would be the case when Hill cattle are used in India. Moreover, on account
of the sacredness of cattle in India, it is eminently desirable to avoid bleeding
this animal to death, but if the amount taken is so regulated as to allow of the
animal going back to his stall and living for a time at least, but very little
blood is obtained and the number of animals sacrificed is greatly increased.
Fortunately, a method of overcoming both these objections has
been put up into pratice with most satisfactory results. It consists simply in
the injection into the jugular vein, after taking as much blood as is required,
of an equal quantity of sterilised salt solution of the same specific gravity as the
blood itself, such as is used in the case of transfusion after severe hœmorrhages.
In this way the circulation is restored, and it has been found that 2,000 c.c. of
blood can be easily obtained and still the animal walks back to its stall as if
nothing had been done to it, and in fact animals so treated appear to have a
better chance of recovery from the disease than those which are not bled.
Moreover, two days later the process can be repeated and the same quantity
taken, and yet the animal will again walk back to its stall and often live for some
days longer, although when such large quantities are repeatedly taken, the animal
seldom recovers. In this way much larger quantities of blood can be obtained,