akes. If mucus is
present at the same time, the bile may become so viscid that when it is
poured from one glass to another it forms long bands. The bile in health is
a limpid fluid, containing no solid particles.

If the animal during life has not been observed to pass urine colored with
blood or red water, the bladder should be opened. This quite invariably, in
acute cases, contains urine which varies in color from a deep port wine to
a light claret. In many cases the color is so dense that light will not
pass through even a thin layer. (Pl. XLV, fig. 3.) The kidneys are always
found congested in the acute attack. The disease exerts but little effect
on the stomach and intestines beyond more or less reddening of the mucous
membrane; hence an examination of them may be safely omitted. The lungs
are, as a rule, not diseased. The heart usually shows patches of blood
extravasation on the inside (left ventricle) and less markedly on the outer
surface.

We have observed jaundice of the various tissues but very rarely. It has
been observed by some quite regularly, however.

During the hot season about 90 per cent of the susceptible mature animals
from a noninfected district die, but later, in the cool weather, the
disease assumes a milder type, with a consequent decrease in the number of
deaths.

_The cattle tick, Margaropus annulatus, as the carrier of Texas fever._
(Pls. XLVI, XLVII, and XLVIII.)--The cattle tick is, as its name indicates,
a parasite of cattle in the southern part of the United States. It belongs
to the group of Arthropoda and to the genus _Margaropus_ (or _Boophilus_),
which is included in the order Acarina. Its life history is quite simple
and easily traced from one generation to another. It is essentially a
parasite, attaching itself to the skin (Pl. XLVIII) and drawing the blood
of its host. It is unable to come to maturity and reproduce its kind unless
it becomes attached to the skin of cattle, whence it may obtain its food.

The eggs laid on the ground after the female has dropped from the host
begin to develop at once. When the embryo is fully formed within the shell
it ruptures this and gains its freedom. The time required from the laying
of the eggs to their hatching varies considerably, according to the
temperature. In the laboratory in the heat of midsummer this was
accomplished in about 13 days. In the late fall, under the same conditions,
it required from four to six weeks. The larva after