PATHOGENESIS 117 



to one homogenous mass. This mass is riddled 

 with tracts and under the now unrecognizable 

 hgamentum nucha is an abscess cavity almost 

 closed by granulation tissue. The surface of 

 the atlas is rough from destruction of its peri- 

 osteum and it may be studded by numerous 

 vegetations of bony growths. There is found 

 sometimes a shredded condition of parts of the 

 ligament, parts that have partly loosened from 

 necrosis. In some cases, usually in aged horses, 

 the hgament is permeated with calcareous de- 

 posits, each of which is well incarcerated with 

 connective tissue elements. 



Atypical Poll-Evil 



The atypical poll-evil begins with a halter 

 abrasion of some kind of wound that 

 gives admission to pyogenic microorganisms. 

 It is at first a subcutaneous abscess, 

 and if carbuncular in character may give 

 rise to all of the symptoms of a typical 

 poll-evil in the phlegmonous stage. This 

 form will differ from the typical form in 

 that cicatrization will follow evacuation of its 

 pus and general slough. If deep and the 

 slough should be attached to the ligamentum 

 nuch^e a chronic poll-evil having all of the char- 

 acteristics of the other, the typical kind, will 

 supervene. In this case the ligament is at- 



