412 NAVICULAR DISEASE. 



and narrowed heels of the coffin-bone. There will not be the natural 

 adhesion and strength, and a very shght cause, or even the very habit 

 of contraction, will, in spite of all care and the freedom of the inner 

 quarter, in very many instances cause the foot to wire in again as badly 

 as before. 



NAVICULAR DISEASE. 



Many horses with well-formed and open feet become sadly and perma- 

 nently lame, and veterinary surgeons have been puzzled to discover the 

 cause. The farrier has had his convenient explanation, ' the shoulder ; ' 

 but the scientific practitioner may not have been able to discover an os- 

 tensible cause of lameness in the whole limb. There are few accustomed 

 to horses who do not recollect an instance of this. 



Behind and beneath the lower pastern-bone, and behind and above the 

 heel of the coffin-bone, is a small bone called the navicular or shuttle-bone. 

 It is so placed as to strengthen the union between the lower pastern and the 

 coffin-bone, and to enable the flexor tendon, which passes over it in order 

 to be inserted into the bottom of the coffin-bone, to act "vvith more advan- 

 tage. It forms a kind of joint with that tendon. There is a great deal 

 of weight thro"\vn on the navicular bone, and from the navicular bone on 

 the tendon ; and there is a great deal of motion or play between them in 

 the bending and extension of the pasterns. 



IS'umerous dissections have shown that this joint, formed by the tendon 

 and the bone, has been the frequent, and the almost invariable, seat of this 

 obscure lameness. The membrane covering the cartilage of the bone has 

 been found in an ulcerated state ; the cartilage itself has been ulcerated 

 and eaten away ; the bone has become carious or decayed, this caries, or 

 decay, however, does not occur in that surface of the bone forming a portion 

 of the coffin-joint — but on that surface over which the flexor tendon passes, 

 and as the disease progresses, the tendon itself becomes much attenuated. 

 Navicular disease is seldom met with in young horses, or those employed 

 for slow work, but generally amongst well-bred horses, with strong feet, 

 used for fast purposes on hard ground. 



Stable management has little to do with the production of this disease, 

 any farther than if a horse stands idle in the stable several days, and the 

 structure of the foot, and all the apparatus connected with motion, become 

 unused to exertion, and indisposed for it, and he is then suddenly and 

 violently exercised, these parts are very liable to be bruised and injured. 

 This, amongst other evils, will be lessened by a loose box, in which a horse 

 will always take some exercise. 



Amongst the predisposing causes, none ought to be more thoroughly 

 known than that navicular disease is hereditary in its nature, and there 

 cannot be a surer method of propagating this destructive disease than 

 breeding from parents afflicted with it. The exciting cause is usually 

 violence applied to the part the result of concussion. By this means in- 

 flammation is set up in the tissue of the navicular bone, wliich leads to 

 ulceration and destruction of a portion of the cartilage covering its surface. 

 As a result of this, the flexor tendon will be in contact with an ulcerated 

 rough surface, instead of the beautifully smooth and elastic one, when free 

 from disease. The ulceration always takes place on the lower surface of 

 the navicular bone, and usually first exhibits itself on the convexity in the 

 centre of the bone. The disease is nearly always confined to the fore-feet, 

 and is generally slow in its progress, although in some instances great 

 concussion has caused rapid ulceration. 



The symptoms by which this disease vnW be recognised are not very 

 distinct, especially in the early stages. There is slight lameness at start- 



