184 Veterinary Medicine. 



angle of the lower jaw, by a poke worn in pasture by the horse, 

 or by stanchions in the cow. Hogs may suffer from blows of the 

 triangular neck gear worn to prevent them from breaking through 

 fences. Blows by the yoke, incised and contused wounds implicat- 

 ing the nerve, such as neurectomy, and the blows received in in- 

 terfering, and compression by tumors or bony growths, are 

 familiar examples. Fractures with displacement, notably those 

 of the sacrum and proximal end of the coccyx with caudal paraly- 

 sis, are not uncommon. In fractures of the limbs the pressure 

 upon or wounding of a nerve. Again, the callus on the seat of 

 fracture may induce neuritis by pressure as may also the projec- 

 tion of the end of a bone in luxation. Rheumatism affecting the 

 nerve sheaths and, in birds and swine, gout, are additional 

 factors. Violent overdistension, and even chronic muscular 

 spasm, are quoted as causes. 



Lesions. The early changes are mainly in the connective tissue 

 sheath, which becomes hypersemic, red and swollen, with a gela- 

 tinoid exudate and a great multiplication of leucocytes. I^ater, 

 the interfibrillar connective tissue is involved and the nervous 

 substance proper undergoes hyperaemia and degeneration. The 

 axis cylinder undergoes granular degeneration and the myelin 

 breaks up into oil-like globules. The lesions are at first limited 

 in extent, though there may be more than one focus, and the re- 

 sulting degeneration of the nervous filaments advances toward 

 the periphery in accordance with Waller's law by which disease 

 changes proceed rapidly in parts cut off from their trophic cells. 



The muscles supplied by the inflamed nerves also rapidly 

 degenerate. The fibres shrink in size, and lose their striated 

 appearance, becoming distinctly granular, and pale. Round cells 

 are formed in excess in the sarcolemma and muscular fibre, and if 

 the morbid condition persists there is fibroid degeneration, cir- 

 rhosis and contraction. 



Symptoms. In the absence of the subjective element of pain, 

 which is the most constant symptom in man, we must rely mainly 

 on the exquisite tenderness on pressure along the line of the 

 nerve, but localized at some particular point, on the swelling at 

 such tender point and on the loss of muscular power or even of 

 sensation in the tissues corresponding to its peripheral distribu- 

 tion. The muscles may be hypersensitive and are usually flaccid 



