PATHOGENESIS 53 
because the cavity, pointing upward, does not 
drain and the pus-soaked dead elements of the 
ligament remaining stubbornly attached to the 
living, favor the gradual onward march of the 
process of destruction. Those originating pos- 
teriorly travel forward into the ligamentum 
nuche under the connective tissue of the mane 
and thus seat themselves at just the same point 
as the atypical form, the chief difference being 
the amount of bone involvement, which in the 
atypical form is always more pronounced than 
in the other. Beginning at the highest point 
of the withers from a serious pressure necrosis 
from the harness, this form is more prone to 
travel downward into the spines, ofttimes at- 
tacking two or more of them with an acute 
destructive osteitis that travels down toward 
the bodies of the vertebre casting off se- 
questra and fusing them together with a mass 
of connective tissue that is very slow to recon- 
nect itself to the surrounding integuments, 
even after the pathological process has other- 
wise terminated. sg 
The disease is most common in horses whose 
withers are thin of flesh from hard work and 
privation. The vitality thus reduced is a dom- 
inating etiological factor. The enfeebled tissue 
becomes the prey of the virulent infection in- 
troduced through and harbored by the harness 
