ENLARGEMENT OF SYNOVIAL CAVITIES IN FORE LIMB. 
555 
(C) Distension of the sheaths of extensor tendons. Of the many 
varieties the most important are :— 
(1) Distension of the sheath of the extensor suffraginis in the carpal 
region. This consists of a swelling as large as a goose’s egg, which 
appears B to 4 inches above the knee, and beginning on the outside, 
extends downwards; in some cases it may even encroach on the front 
of the joints (figs. 20B and 204, e). 
(2) Distension of the sheath of the extensor tendons in front of the 
carpal joint. The extensor pedis, extensor suffraginis, and extensor 
metacarpi are provided with sheaths in front of the knee. These 
sheaths may be mechanically injured, as already pointed out (see 
“ Injuries to the Knee”), but often become distended. The following 
are the chief seats of such “ galls ” :— 
(a) The sheath of the extensor pedis, which begins 6 inches above 
the knee-joint, passes through the outer furrow in the lower end of the 
radius, and over the front of the carpus as far as the upper end of the 
metacarpus (figs. 20B and 204,/). On account of its being clothed in a 
strong fascia, dropsy of this sheath seldom occurs. 
( b ) The extensor metacarpi has, at the same height, a sheath which 
passes through the middle furrow in the radius, and extends as far as 
the lower row of carpal bones (figs. 203 and 204, g). 
(c) The sheath of the extensor metacarpi obliquus begins on the 
outside, B inches above the knee, passes obliquely downwards and 
inwards over the anterior surface of the joint as far as the head of the 
inner small metacarpal (figs. 20B and 204, h). Distension of this sheath 
produces a sausage-shaped swelling, extending in an oblique direction 
as described, and divided by the extensor pedis into several portions. 
(c?) The bursa for the extensor pedis lies above the fetlock-joint on the 
anterior surface of the metacarpus. Its upper or anterior wall is formed 
by the tendon of the extensor pedis (fig. 203, i). When healthy it is 
from § to 1 inch long, and -§ to J inch broad, but when diseased, may 
form a swelling larger, than a goose’s egg, lying on the anterior surface 
of the metacarpus, just above the fetlock-joint. This bursa sometimes 
communicates with the fetlock-joint. To shorten description, the 
following classification has been adopted:— 
(I.) Bursal enlargements on the front of the knee-joint and on the 
fetlock-joint. 
(II.) Bursal enlargements on the outer surface of the knee and so- 
called “wind galls.” 
(III.) Enlargements of sheaths of extensor tendons in the carpal region. 
These last may again be divided into— 
(a) Superior—sheath of extensor suffraginis above the knee-joint. 
(b) External—sheath of extensor pedis. 
