360 VETERINARY PATIIOLUGV. 



small round cells, the production of endotheloid and giant cells by 

 the invaded tissue, and finally the development of a fibrous cap- 

 sule around the entire mass. The fungus may appear in the be- 

 ginning as mycelial elements, but later it has the typical rayed 

 appearance. In old lesions the central portion or body of the 

 fungus becomes calcified. 



Surrounding the clubs or mycelium in the early stages are 

 var3-ing numbers of small, round cells (lymphoc}-tes) . 



As the disease pro'^resses, the matured fungus is more or 

 less surrounded bv giant cells that actually contact the fungus. 

 The actinomycotic giant cell is very irregular in shape and size 

 and has \-arving num])ers of nuclei scattered indiscriminately 

 throughciut the cell body. 



Endotheloid cells appear marginallv to the giant cells. These 

 cells are similar in appearance to the endotheloid cell of tuber- 

 culosis, ha\-ing a relati\'elv large cell l)od^' and a small, single 

 nucleus. 



The small, round cells are first noticed immediately around 

 the fungus, but later thev infiltrate the surrounding tissue also, 

 and are in excess of all other cells in the lesion. 



Fibroblasts appear in the margin (jf the early lesion, and 

 through their activitv a thick fibrous capsule is produced. 



Actinomycotic pus is found to be composed of tissue shreds 

 and fragments, lymphoid cells and some ])olymorphonuclear 

 leucocytes, an occasional endotheloid cell and the Cladothrix 

 actinomyces. 



Extension. — The extension of actinomycosis has usually been 

 described as taking place only by growth in continuitv or contig- 

 uity, or by passing along the respiratory, digestive or genito- 

 urinary tubes. By a careful observation of over 72,000 cattle 

 slaughtered, it has been found that manv cases, in which there 

 were "hair sores" but no actinomycotic tongue lesions, showed 

 actinomycosis of the sulimaxillar}^ lymph nodes. The majority 

 of cases of lingual actinomycosis are accompanied bv involve- 

 ment of the submaxillary lymph nodes. That practically all 

 cases of actinomycosis of the submaxillarv lymph nodes occurred 

 in animals having "hair sores'' is indicative of lymphatic exten- 

 sion. It is therefore quite probable that actinomycosis may be 

 extended in the animal bodv bv means of the lymph. 



Differential Diagnosis. — Bovine actinomycosis may be con- 

 founded with tuberculosis, nodtilar disease, abscess formation 

 and various tumors. 



Tubercular lesions calcify, actinomycotic lesions rarch' be- 



e calcified. Tubercular pus is usually quite dififerent from 



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