430 DISEASES OF THE HORSE’S FOOT 
then progressed until destruction of the secreting layer of 
the bursal membrane has been seriously interfered with, 
and in this case we find a distinct deficiency in the quantity 
of synovia in the bursa. In advanced cases it is even 
found that the bursa is absolutely dry. 
2. Changes in the Cartilage.—Directly that portion of the 
bursal membrane covering the cartilage is the subject of 
inflammatory change, the cartilage itself, by reason of its 
low vitality, soon suffers. 
Under a process, which we may term ‘dry ulcerative,’ 
the cartilage covering the ridge on the lower surface of the 
bone commences to become eroded, and in appearance has 
been likened, both by English and Continental writers, to a 
piece of wood that has been worm-eaten (see Fig. 161). 
Fic. 161.—Navicuntar Boner (POSTERO-INFERIOR SURFACE) SHOWING 
THE ‘ WORM-EATEN’ APPEARANCE CAUSED BY EROSION OF THE 
HYALINE CARTILAGE, AND COMMENCING RAREFACTIVE ARTHRITIS. 
‘ At this stage, or much earlier ’—we are quoting Colonel 
Smith, A.V.D.—‘ may be found calcareous deposits in the 
fibro-cartilage and the bone. They are scattered like fine 
sand here and there, generally across the inferior half of 
the face of the bone; they are sometimes numerous, 
frequently scanty, occasionally entirely absent. The 
amount of calcareous degeneration depends upon the 
lesions present. If much destruction of bone exists, there 
will be but few calcareous deposits; whilst if there are 
many calcareous deposits, there may be but slight ulcera- 
tion of bone tissue, and perhaps none at all. In fact, I 
have held the opinion, and see no reason to modify it, that 
calcareous deposits are safeguards against caries.’ * 
* Journal of Comparative Pathology and Therapeutics, vol. vi., 
p. 195. 
