PATHOGENESIS 41 
liniments and blisters applied to them often 
are credited with curative properties when, in 
fact, it was an inherent influence that operated 
to that end. 
The duration of this stage has been very 
difficult for us to determine. We believe, how- 
ever, that it is very irregular, that some cases 
develop very rapidly into clinical cases while 
others remain almost dormant for months, 
some disappearing entirely and some bulging 
slowly toward the surface. 
It is these slowly forming ones that develop 
so much fibrous tissue and thus change the en- 
tire aspect of the condition from cyst to neo- 
plasm. This occurrence seems almost sufficient 
reason to include in the classification a third 
form of fistula of the withers—the fibrous 
form—if the reader were not familiar with the 
remarkable aptitude of horse-flesh to form 
fibrous tissue from continued irritation. 
Edema, pressure, foreign body, feebly virulent 
infection, cold abscess, granuloma and other 
tumors in the flesh of horses cause the forma- 
tion of great volumes of fibrous tissue unlike 
that of any other animal. It is thus that a 
slowly forming fistula beginning in the depths 
of the neck becomes the underlying cause of 
the formation of new tissue in such abundance 
