217 
OBSERVATIONS ON THOROUGH-PIN. 
By J. H. B. HALLEN, V.S., M.V.C., Edinburgh. 
To the Editor of " The Veterinarian .” 
Sir,— In The Veterinarian issued for the present month, 
there is an article on Thorough-pin, in which the author makes 
statements with regard to the pathology of the disease, and ana¬ 
tomy of the parts involved in it, so utterly at variance with what 
actual dissection and practical experience have taught me regarding 
it, that I beg to trouble you with the following remarks:— 
If it be deemed presumptuous in such a comparatively young 
member of the profession as myself to differ so widely, as I feel 
bound to do, from a professed author, such as Mr. Percivall, I hold 
myself excused from apology in consequence of the importance 
which attaches to the subject in question. 
Without any further prefatory observations, I will enter upon 
the subject I am about to consider, and will direct attention to Mr. 
Percivall’s description of the pathology of thorough-pin. He 
states, “ The pathology of thorough-pin is analogous to that of 
bog-spavin. It consists in anormal accumulation of synovia in the 
joint of the hock, and consequent dilatation and bulging of the cap¬ 
sular ligament.” From this statement, we may infer that tho¬ 
rough-pin is always the effect of bog-spavin; for in another sen¬ 
tence is found—“ But thorough-pin is rarely or never seen without 
bog*spavin, although bog-spavin, in the majority of instances, is 
unattended by thorough-pin.” It is here that my ideas are so 
directl}' opposed to those of Mr. Percivall’s; and it now remains 
for me to state my opinions. In the first place, I believe that bog- 
spavin is, in the majority of cases, attended more or less by tho¬ 
rough-pin : on the other hand, I am also convinced that thorough- 
pin often exists without any bog-spavin. And I will, by permis¬ 
sion, make use of Mr. Percivall’s own words, and state that “ the 
pathology of thorough-pin will explain this seeming paradox.” It 
is, no doubt, perfectly true that any cause leading to the produc¬ 
tion of an increased secretion of synovia in the true hock-joint, and 
that cause existing for any length of time, increased secretion will 
constitute sooner or later bog-spavin. This over-distention of the 
capsular ligament will manifest itself in those situations which 
from their structure permit of it; hence we find it appearing at the 
anterior and inner side of the hock at first, and, if the cause con¬ 
tinues in operation for any length of time, it will also present itself 
at the upper and posterior part of the tarsus. The anterior and 
