i6o

PATHOGENIC BACTERIA.

is much better adapted to the purpose than the anterior.

The introduction of the needle should be made from the

hairy surface of the
ear.

If the ear is manip-
ulated fora moment or
two before the injec-
tion is begun, vaso-
motor dilatation
occurs and the blood-
vessels all become
larger and more con-
spicuous. The vein
should be compressed
at the root of the ear
until the needle is in-
troduced, and the in-

FIG. 41.—Method of making an intravenous jectlOll made as near
injection into a rabbit. Observe that the needle ^^ ^^ ag pQ^b]^
enters the posterior vein from the hairy surface. ,_._ . - . "

The introduction of

bacteria into the lymphatics is only possible by injecting
liquid preparations of them into some organ with com-
paratively few blood-vessels and large numbers of lym-
phatics. The testicle is best adapted to this purpose, the
needle being introduced deeply into the organ.

Sometimes the inoculation can be made by the platinum
wire, a very small opening made in the skin by a snip of
the scissors being sufficient.

Sometimes intra-abdorninal and intra-pleural injections
are made, and in cases where it becomes necessary to
determine the presence or absence of tuberculosis or
glanders in tissues it may be necessary to introduce small
pieces of the suspected tissue under the skin or into the
abdominal cavities. To do this is not difficult. The
hair is carefully, closely cut over the point of election,
which is generally on the abdomen near the groin, the
skin picked up with forceps, a snip made through it,
and the points of the scissors introduced for half an inch