NAVICULAK DISEASE AND NETJKOTOMY. 
681 
The *parts involved are those forming the navicular joint; 
viz., the plantar aponeurosis or expansion of the perforans 
tendon where it passes over the navicular bone ; the postero¬ 
lateral ligaments, including the elastic fibrous cord that forms 
the complementary cushion of the navicular bone ; the antero¬ 
lateral ligaments; the interosseous ligaments; the synovial 
membranes ; the nerves supplying the region; the navicular 
bone; and in some cases, more or less all surrounding parts. 
The morbid anatomy developing in these tissues depends- 
somewhat upon the severity of the cause, but more upon the 
age of the case. 
The causes that I wish to bring to your notice and consid¬ 
eration are concussion and rheumatism. The fore feet of a 
horse are intended more to carry the body than to propel it, 
and the higher action of them is conducive to more bruising 
than is ever seen in the hind feet. This bruising produces a 
subacute inflammation in some of the tissues of the navicular 
region, which induces a favoring of the affected foot; this leads 
on to contraction of the hoof, and if the horse is kept at work 
it will run into a confirmed case of navicularthritis, with all of 
the symptoms and morbid anatomy that are so well known to 
you, as existing in old, useless cripples of this kind. 
Rheumatism may attack the nerves of the feet, owing to 
their great exposure to cold and dampness, and more especial¬ 
ly when sore from previous bruising, which I think will account 
for its prevalence in the fore and its rarity in the hind feet. 
The rheumatic complication tends to confirm the case, and 
gives rise to some peculiar symptoms seen in the early stage 
of the disease, and plays an important part in the subsequent 
development of the more extensive and severe form that leads 
on to complete crippling of the horse. The bruising of the 
navicular tissues may occur from long continued pounding on 
hard smooth road, such as our boulevards and race tracks, 
and accidental pounding of the frog upon cobble stones, car 
tracks, etc.; then when there is a rheumatic tendency in the 
animal the rheumatism always locates in the sore part. The 
early symptoms are obscure, and when not understood, make 
the case a very puzzling one to locate, but when one is famil- 
