cysts in the immediately adjacent
mesentery. The presence of these cysts may give rise to considerable
speculation at the post-mortem.

The ~Pigeon~ may be infected by _Haemosporidia_, and its blood show the
presence of halteridia. This bird may also be the subject of a bacterial
infection known as pigeon diphtheria; while the fowl may be subject to
scabies and ringworm, or suffer from fowl cholera or fowl
septicaemia--infections due to members of the haemorrhagic septicaemia
group.

~Weighing.~--The larger animals are most conveniently weighed in a decimal
scale provided with a metal cage for their reception instead of the
ordinary pan (Fig. 166). Mice and rats are weighed in a modification of
the letter balance, weighing to 250 grammes, which has a conical wire
cage, (carefully counterpoised) substituted for its original pan (Fig.
167).

[Illustration: FIG. 166.--Rabbit scales.]

~Temperature.~--To take the rectal temperature of any of the laboratory
animals, the animal should be carefully and firmly held by an assistant.
Introduce the bulb of an ordinary clinical thermometer, well greased
with vaseline, just within the sphincter ani. Allow it to remain in this
position for a few seconds, and then push it on gently and steadily
until the entire bulb and part of the stem, as far as the constriction,
have passed into the rectum. Three to five minutes later, the time
varying of course with the sensibility of the thermometer used, withdraw
the instrument and take the reading. The thermometers employed for
recording temperature should be verified from time to time by comparison
with a standard Kew certified Thermometer kept in the laboratory for
that purpose.

[Illustration: FIG. 167.--Mouse scales]

~Cages.~--During the period which elapses between inoculation and death,
or complete recovery, the experimental animals must be kept in suitable
receptacles which can easily be kept clean and readily disinfected.

The _mouse_ is usually stored in a glass jar (Fig. 168) 11 cm. high and
11 cm. in diameter, closed by a wire gauze cover which is weighted with
lead or fastened to the mouth of the jar by a bayonet catch. A small
oblong label, 5 cm. by 2.5 cm., sand-blasted on the side of the
cylinder, is a very convenient device as notes made upon this with an
ordinary lead pencil show up well and only require the use of a damp
cloth to remove them (Fig. 168).

The _rat_ is kept under observation in a glass jar similar, bu