PATHOGENESIS 
There are two kinds of fistule of the 
withers. One is the typical or idiopathic form 
and the other is the atypical, traumatic or 
symptomatic form. The first or typical has its 
origin in the development of a serous sac or 
cyst under the ligamentum nuche at the level 
of the second or third dorsal spines, while the 
second or atypical is caused by an external 
wound that serves as a portal of entrance for 
microorganisms. In the first stages these two 
forms differ very materially in every respect 
but in the final stage they are alike in that both 
of them cause disease of the lhgamentum 
nuche or its backward extension (the supra- 
spinous ligament) and sometimes the spines of 
the vertebra themselves. In short, each form 
finally plays the same havoc upon these struc- 
tures, although they have an entirely different 
pathology at the beginning. Fistula of the 
withers in the final stage might be properly 
called necrosis of the ligamentum nuchae or of 
the supraspinous ligament according to its 
cephalo-caudal location. In the typical form 
it is the ligamentum nuche that is chiefly 
affected while the traumatic form, being 
