358 VETERINARY PATHOLOGY. 



sions produced by the stubble. Abrasions resulting from rub- 

 bing on stanchions and feed boxes may be a source of infection in 

 dairy cattle. 



Lesions. — Macroscopic. — Actinomycotic lesions may be sur- 

 face or subsurface. The fungus may invade and produce the 

 lesion in anv tissue. 



Surface lesions begin as small inflammatory centers which 

 usually thicken and become elevated above the general surface. 

 The lesion gradually increases in size, and in some cases assumes 

 a fungoid appearance. At this stage the lesions vary in size from 

 a small pea to a walnut. The surface tissue may become eroded 

 as a result of the extension of necrosis from the lesion and the 

 typical actinomycotic pus discliarged or more frequently the 

 lesion becomes encapsulated by tlie formation of a dense fibrous 

 capsule. The capsule usually limits the development of the lesion 

 and it ma)- 1)e diminished in size by the contraction of the fibrous 

 tissue constituting the capsule. 



Subsurface lesions, thougli l)eginning as inflammatory centers, 

 are invarial^lv Icircumscribed l)y a dense, fibrous wall. As 

 the disease progresses the center (if the lesion undergoes licjue- 

 fving necrosis. The necrosis extends, producing irregular, tor- 

 turius sinuses tliat mav extend through the capsule and into the 

 surrounding normal tissue. I'ltimately the liquified' necrotic 

 tissue (pus) wiiuld ordinarilv 1:)C discharged upon a surface, or 

 the fungus contained in the necrotic tissue (pus) would perfor- 

 ate the primary capsule and cause the production of a secondary 

 fibrous ca])sulc. Thus the lesion is frequentlv composed of sev- 

 eral communicating cavities (multilocular) containing actinomy- 

 cotic pus. Tf such a lesion is incised and pressure applied the 

 t^'pical beads of actinomvcotic pus will appear in A^arious 

 places upon the cut surface. Actinomycotic pus is creamy, 

 stickv, tenacious, vellowish-white and contains small, vellow, 

 grittv granules. The pus has a greasy feel and may have a 

 slight odor. If the pus is permanently maintained within the 

 capsule, its fluid content is absorl^ed and becomes caseous. 



Osseous actinomycosis is of common occurrence. The fungus 

 having gained entrance produces inflammation, which is suc- 

 ceeded by disintegration of the osseous tissue and the formation 

 of cavities or pockets. By growth and extension of the infect- 

 ing fungus, inflammatirin and disintegration is favored, and thus 

 communicating cavities are formed in the afTected bone. As the 

 process of rarefaction continues within there is new osseous tis- 

 sue deposited without. Thus bone affected with actinomycosis 



