ANATOMY AND PHYSIOLOGY OP THE HOUSERS FOOT. 363 
which was in these places altered in colour, very thin and 
soft, or had all but disappeared. 
The fibres of the tendon were not abraded, for the simple 
reason that these osseous particles were yet covered by the 
membrane — each was a “ velvety osteophyte ; }i nevertheless, 
the portions of the tendon in contact with them were under- 
going a change of colour and consistency. In the other foot 
the alteration had considerably advanced, the whole of the 
lower two-thirds of the membrane was more or less the seat 
of ossific transformation ; a prominent, but narrow and 
jagged, deposit had taken place across the transverse ridge 
in the middle of its lower half ; on each side of the ridge 
were fine but sharp granules, and at the lower margin of the 
bone, on one side, was an irregular circle larger than the 
diameter of a pea, from the middle of which the membrane, 
usually rather thick at this part, had been removed ; a mass 
of bony matter had been deposited in a portion of the cavity, 
and extended for some distance into the interosseous or infe- 
rior ligament of the navicular bone, and the compact tissue 
was becoming carious in one or two minute points ; the mem- 
brane had also entirely disappeared from the surface of these 
deposits, but around them it was thickened and soft, and 
evidently in a state of disintegration. On the face of the 
tendon corresponding to the thin sharp lamella across the 
ridge, the fibres were cut to some depth, and in other points 
in contact with the miniature osteophytes they were broken 
and altered in texture and colour. Where they were not 
broken they showed the imprint of the rugosity. Neither 
of these bones offered any pathological change in their can- 
cellated structure, and the compact tissue was only involved 
very superficially at the points where this deposition was 
taking place. The animal had, no doubt, been lame, particu- 
larly in the last- mentioned foot, and the hoofs afforded 
evidence of this from their soles having been pared very thin 
and protected by leather and tar and tow. 
That the malady known as “ navicularthritis” commences, 
in the great majority of instances, on the inferior face of the 
navicular bone, and in its fibro- cartilaginous covering, I enter- 
tain no doubt whatever ; the microscope — that invaluable aid 
to the pathologist — so far as I have employed it, settles that 
matter. I have never been able to satisfy myself that the 
disease began in the interior of the bone ; all my examina- 
tions — and they have been numerous — of bones, in every 
stage of the malady, have been adverse to such a conclusion. 
The histological anatomy of this region would, a priori, 
almost lead to the inference that disease would be much 
