22 FISTULA AND POLL-EVIL 
vicis, posteriorly by the serratus thoracis and 
the scapular cartilage. Its floor is formed by 
the longissimus dorsi and its roof by the trap- 
ezius and rhomboideus. The central partition 
is constituted of the dorsal spines, spinalis dorsi 
posteriorly and the lamellar portion of the 
ligamentum nuche covered with the com- 
plexus anteriorly. The bottom of the trough 
which must be reached for effectual drainage 
can be penetrated only with difficulty and the 
risk of inviting complications in structures not 
previously implicated. Furthermore, these 
muscles being in constant use in locomotion, 
respiratory acts and movements of the neck, 
tend to encourage the burrowing of pus into 
still more inaccessible recesses. 
Thus we find the musculature of primal im- 
portance in any study of fistula of the withers. 
It bounds initial abscess cavities in places 
difficult of access for drainage, they move upon 
each other and favor the distribution of puru- 
lent products into new fields, where secondary 
abscesses are formed, and it exhibits a remark- 
able trend toward fibrosis under the influence 
of the chronic inflammation of adjacent parts. 
The Ligaments 
The ligaments implicated in fistula of the 
withers are the ligamentum nuche and the 
