22 
W. BRYDEN. 
and with cases of disease of the navicular bone, for they are 
quite distinct. For example, we find, ist. True navicular 
disease, a gradual contraction of the hoof from bad surround¬ 
ings, and neglect after birth, coupled possibly with some her¬ 
edity ; causing a slow change leading to necrosis , or gradual 
death of the bone. 
2nd. A modified form of the above, hastened by such 
an accident as a prick with a nail that did or did not reach 
the bone. 
3rd. Disease of the navicular bone, from its having been, 
for example, injured by a nail or other instrument, the bone 
itself being penetrated ; inflammation is set up in the cancellated 
structures of both the interior of the bone and the compact struc¬ 
tures at the same time. Here then are three varieties at least: 
In the first, hereditary or acquired predisposition. In the 
second, hereditary or acquired predisposition, coupled with 
accident. In the first and second then we find contraction 
both as a cause and as a result or effect. In the third, accident 
only ; here contraction may only be as a result or effect. 
To some such fine distinctions may appear frivolous, but 
it must be evident that the history of a lame foot is of much 
importance, especially to the breeder; whether the derelict 
hoof is covering a case of true navicular disease, either of 
heredity or of acquired origin, or a case of disease of the 
navicular bone, resulting from an accident or wound, and in¬ 
dependent of the character of the hoof. 
In looking over a recent edition of Prof. Williams’ excel¬ 
lent Book of Surgery, one is surprised at statements like the 
following, on page 333, which must handicap the student in 
the study of such a subject. He says: 
“ Contraction of the hoof is not a cause but an effect of 
disease; an atrophy of the structures contained within the 
< horny box ’ consequent upon diminished functional activity 
and adaptability of the hoof to the atrophied structures which 
it encloses and protects.” 
Continuing, he adds, “ Prof. Dick said there was a kind of 
contraction of the hoof, in fact a natural tendency to this, in the 
domesticated animal arising from a want of moisture when he is 
