36 
AN ESSAY ON CHRONIC PODOTROCHOLITIS. 
remittent with lameness, the local pathological lesions remaining 
the same. In some cases I have met with chronic podotrocholitis 
accompanied with caries of the navicular bone, and other dis- 
orders, although the horses had not shewn lameness before death. 
W e may at any rate regard it as a general rule, that lameness is 
not caused solely by inflammation of the trochlea of the foot; but 
that other circumstances are necessary to its development, its 
aggravation, and its periodical recurrence. This consideration 
brings us back to spavins, and the intermittent character of the 
lameness they occasion ; and, lastly, to the odontalgic pains excited 
by caries of the teeth. Years may pass away without a carious 
tooth becoming manifest ; suddenly a violent pain attacks it, and 
this again ceases, notwithstanding the continuance of the caries. 
In a case of this nature, the caries does not of itself explain the 
odontalgia in a satisfactory manner ; admitting, however, that it 
were so, to what cause must we attribute the regularity of the at- 
tacks of pain, if not to some peculiar dynamic modification of the 
economy ] May not similar modifications be the cause of the in- 
crease, periodical diminution, and intermittence of the lameness, 
in chronic podotrocholitis 1 Is it advancing too much to conclude 
that the pain, the first source of lameness, is but the reflex conse- 
quence of some general modification of the economy, or of some 
other morbid action ] Veterinary pathology furnishes us with 
various instances of local irritations which are but sympathetic 
phenomena. I will cite the irritation of the skin in hydrorachitis 
in sheep, when the animals bite themselves, and gnaw their wool ; 
and epilepsy in pigs, wherein 1 have seen the animals devour their 
fore-legs, &c. These extraordinary phenomena may be compared 
with the observations on the human being made by Brodie*. 
“ A patient,” says Brodie, “ is suddenly attacked during the night 
with violent pains in the feet, while at the same time he has heart- 
burn in the stomach. The pains disappear as soon as the acids 
become neutralized.” He quotes Dr. Wollaston, who, after hav- 
ing taken an ice, experienced dreadful pain in the ancle. On the 
ice being thrown off his stomach by vomiting, he gained imme- 
diate relief. In another individual labouring under stricture of 
the urethra, pain established itself in the instep : the introduction 
of a bougie sufficed to cause it to disappear. 
Prognosis . — Turner designates the navicular disease “the curse 
upon good horseflesh /” a characteristic epitome of its prognosis. 
Chronic podotrocholitis is, in fact, one of the most insidious of 
diseases. Lying latent for a considerable period, all the while 
working destruction, when taken in hand, it resists the healing 
* Brodie’ s Lectures on Diseases of the Nerves. 
