26 FISTULA AND POLL-EVIL 
esses below. ‘The posterior part is attached to 
the second and third dorsal spines and extends 
in the form of several digitations forward and 
downward where its brush-like fibers reach the 
spines of the fifth and sixth cervical segments. 
The fibers of the ligament are more spare than 
in the anterior part and sometimes do not even 
reach the sixth vertebra. Between the anterior 
and the posterior parts is a space of consider- 
able dimensions which especially in horses of 
good flesh contains a mass of fatty tissue. This 
opening is at the level of the extremity of the 
second dorsal spmous process and is the seat 
of typical fistula of the withers. It is the space 
where the sacculation of fistula begins. 
The supraspinous ligament is a structure 
composed of white fibrous tissue and extends 
along the dorsal region to the sacrum. It is 
the continuation of the ligamentum nuche 
posteriorly. A careful dissection of this struc- 
ture fails to show that it begins as an independ- 
ent structure, as its fibers although they change 
in structure from yellow elastic to white fibrous 
tissue, are simply continuations of each other. 
From the surgical standpoint the supraspinous 
ligament and the ligamentum nuche must be 
regarded as a single apparatus which changes 
in the character of its tissue at the crest of the 
withers. Over the crest it is a very thick, dense 
