ease a similar line
of treatment should prove equally efficacious. However, this is not the
fact. On the other hand, the occurrence of osteomalacia on old, worn-out
soil, or on land deficient in lime salts, or from eating feed lacking in
these bone-forming substances, or drinking water with a lime deficiency,
is in perfect accord with our knowledge of the disease. But osteoporosis
may occur on rich, fertile soil, in the most hygienic stables, and in
animals receiving the best of care and of bone-forming feeds with a
proper amount of mineral salts in the drinking water.

_Cause._--The cause of this disease still remains obscure, although
various theories have been advanced, some entirely erroneous, others
more or less plausible; but none of them has been established. Thus the
idea that feeding fodder and cereals poor in mineral salts and grazing
in pastures where the soil is poor in lime and phosphates will cause the
disease has been entirely disproved in many instances. Others have
considered that the disease starts as a muscular rheumatism which is
followed by an inflammatory condition of the bones, terminating in
osteoporosis. The idea that the disease is contagious has been advanced
by many writers, although no causative agent has been isolated. Numerous
experiments have been made by inoculating the blood of an affected horse
into normal horses without results. A piece of bone taken by Pearson
from the diseased lower jaw of a colt was transplanted into a cavity
made for it in the jaw of a normal horse, but without reproducing the
disease. Petrone believes that the _Micrococcus nitrificans_ causes
osteomalacia in man as a result of its producing nitrous acid, which
dissolves the calcareous tissues, and when injected into dogs in pure
culture a similar disease is produced. It is probable that if this work
is confirmed a somewhat similar causative factor will be discovered for
osteoporosis.

Elliott considers the latter disease to be of microbic origin, the
result of climatic conditions, and divides the island of Hawaii into two
districts, in one of which the rainfall is 150 inches annually, where
bighead is very prevalent, and the second of which is dry and rarely
visited by rain, where the disease is unknown. Removal of animals from
the wet to the dry district is followed by immediate improvement and
frequently by recovery. In the wet district horses in both good and bad
stables take the disease, but in the dry distr