146 ON THE NAVICULAR DISEASE AND SPAVIN. 
navicular and hock joints ; and although diseases do occur in 
every joint, yet, by those who have paid much attention to lame¬ 
ness, and had opportunities of making post-mortem examinations, 
I am sure it will be allowed that the lameness in ninety-nine 
cases in every hundred, when no visible alteration of structure is 
present, is attributable to disease, if in the fore legs, in the 
navicular joint; if in the hinder ones, in the hock. 
The diseases of joints in horses are few of them, except in 
farcy, referable, as in the human subject, to constitutional de¬ 
rangement. I have heard it asserted that scrofula does not 
exist in the horse, but I must confess that I never saw a case 
that I could make up my mind to call by such a name. 
I certainly have seen some cases of joint affections that have 
much reminded me of rheumatic swellings ; but there are, I 
believe, no authenticated instances recorded by English writers 
of rheumatism or gout having occurred in the horse; and if the 
latter disease did exist, we should certainly have observed the 
symptoms that attend it, for they are too unequivocal to be mis¬ 
taken. 
But our French brethren, as usual, have not been backward in 
observing gout, rheumatism, scrofula, and even chalk stones in the 
joints. Vitet mentions having discovered, in the hock joints of a 
horse that had been exposed to severe exertion every day, a thick 
fluid of a chalky consistence, but which, he confesses candidly, 
he found it in so small a quantity, and of so doubtful a cha¬ 
racter, that he should have overlooked it, had he not wished to 
establish his opinion that the disease was gout. 
The diseases of joints in the horse, in my opinion, all com¬ 
mence in the same way, and, though not springing from the same 
cause, they are all seated in the same tissue : and though par¬ 
ticular joints may require particular methods of treatment, as 
the navicular joint evidently does, yet, aware that inflammation 
is the precursor of all the subsequent mischief, we are imperatively 
required to employ vigorous means to arrest its baneful progress. 
I repeat, that I believe all navicular diseases to commence in 
an inflammation of the synovial membrane. This delicate 
membrane, which, if we may judge by our own feelings, is ex¬ 
ceedingly sensible when inflamed, is in its natural condition 
almost as transparent as the conjunctiva that covers the cornea: 
but as soon as it becomes inflamed, its vascularity is perceptible, 
and its vessels, filled with red blood, present a scarlet surface, 
and then the functions of the secreting membrane necessarily be¬ 
come altered. 
In those joints in which we have the opportunity of observing 
the progress of inflammation, particularly in the knee-joint, we 
