PART VII. 

 DISEASES OF THE ORGANS OF LOCOMOTION. 



MUSCULAR RHEUMATISM. 



Definition. — Muscular rheumatism is a form of myositis. 



Occurrence. — It is not common in animals. In large animals 

 it is most frequent in horses and cattle. 



Etiology. — ^The causes of muscular rheumatism are 

 unknown. Cold and dampness combined are important but 

 probably only predisposing factors. In all probability the 

 immediate cause is either an infection or ari intoxication 

 although the absence of fever and localization in individual 

 muscles rather speak against this theory. 



Necropsy. — On necropsy the muscles attacked are hyper- 

 emic, hemorrhagic, and show serous exudate and cellular 

 infiltration. In some cases there is cloudy swelling and fatty 

 degeneration of the muscle fibers. In chronic cases a prolif- 

 eration of connective tissue occurs in the muscles attacked. 



Symptoms. — Characteristic of rheumatism is a suddenly 

 appearing, painful condition of certain muscles which usually 

 follows exposure to cold. There is a tendency for the pain 

 to shift from one muscular group to another. The inflam- 

 mation disappears often as suddenly and mysteriously as it 

 came but there is always a tendency to relapses. On palpa- 

 tion the affected muscles feel tense and are very sensitive. 

 Depending upon the location of the inflammation different 

 forms of rheumatisrn are distinguished clinically : 



(a) Shoulder rheumatism (omalgia, which affects the biceps, 

 brachiocephalicus and the supra- and infraspinati muscles 

 causing in horses shoulder lameness of the swinging-leg type. 



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