364 ANATOMY AND PHYSIOLOGY OF THE HORSE’S FOOT. 
more likely to commence on the lower surface than in the 
spongy tissue of the navicular bone ; and pathological 
anatomy proves that it really is so. The spongy tissue is 
only involved when the compact had been destroyed, and 
this may be said to take place towards the later stages of the 
malady.* In fact, it has appeared to me that the membrane 
covering the inferior face of the navicular bone behaves not 
unlike the periosteum covering other bones, and offers the 
same or similar morbid alterations when affected with acute 
or chronic inflammation, and that the bone and tendon are 
only subsequently involved. In some, and by no means rare in- 
stances, nevertheless, I am ready to admit that the tendon may 
be primarily affected, as the result of sudden injury ; the army 
veterinary surgeon has not unfrequently to deal with cases of 
this description. In general, however, navicularthritis is essen- 
tially chronic inflammation of, and osseous deposition in, the 
fibrous membrane; only too often followed by its destruction, 
injury to the tendon, and profound alterations in the texture 
of the lower face of the bone, and, finally, of its interior. The 
molecular death or caries of this face of the bone is a very 
advanced stage of the disease. 
The two articular faces are so seldom involved in disease 
that they may be said to be, as a rule, exempted from its 
ravages. So much is this the case, that in examining feet 
that have been affected with navicularthritis, we do not 
expect to find anything the matter with these surfaces ; 
though of course when the lower face has been destroyed and 
the spongy tissue deeply involved, or when the tendon has 
become seriously and extensively implicated, it is scarcely 
possible that these surfaces can be maintained in health. 
To how great an extent the usual treatment to which 
the horse’s foot is subjected predisposes the fibro-cartilaginous 
membrane covering the lower face of the navicular bone to 
inflammation, those who understand the physiology of that 
organ will be at no loss to comprehend. 
So far, then, as our survey of the horse’s foot has gone, and 
accepting this survey more as a proof of design than perhaps 
as an aid to the prosecution of anatomical or physiological 
knowledge, we might be justified in asserting that in the 
disposition of the bones, ligaments, tendons, and joints, a 
higher degree of constructive wisdom seems to be evinced 
* It lias been recently stated that this disease usually commences in the 
centre of the bone, where the nutrient action is supposed to be lowest. A 
glance at the interior of the bone, and particularly if it be an injected 
specimen, will show that the centre of the most vascular portion. Can we, 
then, receive the statement that the nutrient action is lowest there F 
