es,
stained with methylene blue, within the red corpuscles. The larger body on
the right _b_ is a white blood corpuscle, also stained with methylene blue.
(Magnified 1,000 diameters.)

PLATE XLVI. The cattle tick (_Margaropus annulatus_), the carrier
of Texas fever.

Fig. 1. A series of ticks, natural size, from the smallest, just hatched
from the egg, to the mature female, ready to drop off and lay eggs.

Fig. 2. Eggs, magnified 5 times.

Fig. 3. The young tick just hatched (magnified 40 times).

Fig. 4. The male after the last molt (magnified 10 times).

Fig. 5. The female after the last molt (magnified 10 times).

Fig. 6. A portion of the skin of the udder, showing the small ticks. From a
fatal case of Texas fever produced by placing young ticks on the animal.
(Natural size.)

Fig. 7. A portion of the ear of the same animal, showing same full-grown
ticks ready to drop off. (Natural size.)

PLATE XLVII. The cattle tick (_Margaropus annulatus_).

Fig. 1. Dorsal view of male. (Greatly enlarged. Original.)

Fig. 2. Ventral view of male. (Greatly enlarged. Original.)

Fig. 3. Dorsal view of replete female. (Greatly enlarged. Original.)

Fig. 4. Ventral view of same.

PLATE XLVIII. Portion of a steer's hide, showing the Texas-fever
tick (_Margaropus annulatus_). (Natural size. Original.)

PLATE XLIX. Fig. 1. Tick-infested steer.

Fig. 2. Dipping cattle to kill ticks.

PLATE L. Facsimile of poster used to show the difference between
cattle of similar breeding raised on a tick-free farm in one case and on a
ticky farm in the other.

* * * * *

CHRONIC BACTERIAL DYSENTERY.

Chronic bacterial dysentery is a chronic infectious disease of bovines
caused by an acid-fast bacillus simulating the tubercle bacillus and
characterized by marked diarrhea, anemia, and emaciation, terminating in
death.

This disease was observed in the United States for the first time by
Pearson in Pennsylvania cattle, and later by Mohler in Virginia cattle, and
in an imported heifer from the island of Jersey at the Athenia quarantine
station of the Bureau of Animal Industry.

Pearson proposed the name chronic bacterial dysentery for this affection,
and it has also been termed Johne's disease, chronic bacterial enteritis,
chronic hypertrophic enteritis, and chronic bovine pseudotuberculous
enteritis by various European investigators. The disease was first studied
in 1895 by Johne and Frothingham in