PATHOGENESIS 



There are two kinds of fistulce of the 

 withers. One is the tijpical 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 nuch« 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 tw^o 

 forms differ very materially in every respect 

 but in the final stage they are alike in that both 

 of them cause disease of the ligamentum 

 nuch« 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 nuchae that is chiefly 

 affected while the traumatic form, being 



