actures are not uncommon in consequence of
attempts to arise, which complications, in addition to emaciation,
result in death.

The disease may exist in this manner for variable periods extending from
two or three months to two years. The termination of the disease is
uncertain at best, but is likely to be favorable if treatment and a
change of feed, water, and location is adopted in the early stages of
the malady.

_Lesions._--As has been stated, the bones are the principal tissues
involved. The nutrition of the bone is disturbed, as is indicated by the
diminished density or rarefaction of the bony substances, the increase
in the size or widening of the Haversian canal and the medullary cavity,
and the enlargement of the network of spaces in the spongy tissue, the
absorptive changes following the course of the Haversian system. In this
process of absorption there are formed within the substance of the bone
areas of erosion, indentations, or hollow spaces of irregular shape.
These spaces increase in size and become confluent, causing an
appearance resembling some varieties of coral. The affected bone may be
readily incised with a knife, the cut surface appearing finely porous.
This porous area is soft, pliable, and yields easily to the pressure of
the finger. It has been shown by chemical analysis that the bone of an
osteoporotic horse, when compared with that of a normal horse, shows a
reduction in the amount of fat, phosphoric acid, lime, and soda, but a
slight increase in organic matter and silicic acid. The bones lose their
yellowish-white appearance, becoming gray and brittle. The affected
bones may be those of any region or portion of the body. Besides the
change already noted in the bones of the face, the ends of the long
bones, such as the ribs, are involved, and may be sectioned, though not
so readily as the facial bones. The bones of the vertebrae are also
frequently involved, necessitating great care in casting a horse, as the
writer has seen several cases of broken backs in casting such animals
for other operations. The marrow and cancellated tissue of the long
bones may contain hemorrhages and soft gelatinous material or coagulated
fibrin. The internal organs are usually normal, but a catarrhal
condition of the gastrointestinal tract may be noted as the result of
the improper mastication, resulting from the enlargement of the jaws and
soreness of the teeth.

_Treatment._--The affected animal should be im