LAMINITII5 AND NAVICULAR DISEASE. 815 
Now, let us bring sound physiological doctrines to our aid, 
and let the first question we ask ourselves be— 
What are Hereditary lendencies ? 
Medically speaking, it may be proper to define them as 
“ a strong proneness in the constitution to assume the same 
characteristics that existed in one or both of the parents/* 
It will be perceived that this definition will comprise the 
mental as well as physical peculiarities, the excellences as 
well as the defects in the constitution, as I take it for 
granted it is a conceded point that numerous satisfactory 
examples can be adduced of excellence and talent as well as 
of the weaknesses and vices of the parents being transmitted 
to their offspring. Animals may be born free from disease, 
but with peculiar textures in certain localities of such imper¬ 
fect kind as to become morbidly affected by causes which 
would produce no effect whatever on limbs or textures 
soundly and normally developed. Whenever any special 
organisms undergo a change, such, for instance, as bone 
becoming soft, or cellular membrane becoming scirrhous, 
such changes depend entirely upon organic combination; 
some special elements have been withdrawn, or have been 
introduced into it; for aught we know, the carbon, oxygen, 
hydrogen, and various earthy matters, have varied in their 
proportions, and, been so arranged, that they have created 
the developments nature is silently but irresistibly working out, 
and this, too, wholly and entirely irrespective of any particular 
conformation whatever as a predisposing cause. All physio¬ 
logists know* that the body I possess to-day is an entirely 
different body to that which I possessed a few years ago, 
and that every atom of the structures of which this body is 
composed to-day will be totally and entirely changed in a 
few years hence, if I am still in existence. Decay and repro¬ 
duction are actions constantly going on in every living body; 
as an apposite example, if you crush your thumb-nail, and 
it comes off, you will find in eight or nine months an entire 
new nail will have been produced ; it would have been repro¬ 
duced the same if the old nail had not been crushed off; it is 
nature*s process, an inflexible condition of vitality going on 
throughout the entire constitution. But what of the idiosyn¬ 
crasies? They continue to operate in their own secret, 
silent, mysterious, but never-varying courses. It is very 
questionable to my mind whether any known method of 
treatment can possibly prohibit the development or natural 
progress of any morbid condition in its legitimate locality; 
