884 EXZOOTIC PARAPLEGIA. 



does not exist except in a few of the most severe cases, and 

 then only very slightly. The symptoms of illness in those 

 cases where the cerebral structures are aflected are, as a rule, 

 developed very rapidly ; in the condition where want of muscular 

 power of the posterior extremities is the diagnostic symptom, 

 the evidences of disease are gradual in development. 



The after-death appearances in the one affection, that where 

 the cerebral symptoms are dominant, are congestion or inflam- 

 mation of the cerebral membranes, with the attendant results 

 of such morbid activities. In the purely paraplegic form the 

 chief or only lesions of the nervous system are associated with 

 the cord, which in many cases is the opposite of hypera^mic. 

 Blood-letting, in the form with marked cerebral symptoms, 

 is invariably productive of good ; in enzootic paraplegia it is 

 attended with the opposite results. 



This form of reflex or sympathetic paraplegia, with which 

 we are now dealing, besides arising less, or probably not at all, 

 from the quantity of food taken, being dependent for its origin 

 rather on its character or speciality, is occasionally extensively 

 distributed, but only where horses are depastured on young- 

 grasses, or lands where the rye-grass is more abundant than 

 other forage plants, and at a particular stage of the growth of 

 this plant, and is in some years more troublesome than others. 

 The subjects of its attacks are not of any particular breed or 

 age ; and we find the disease both in stabled and in pastured 

 horses, provided they are exposed to the one disease-inducing 

 factor, feeding on this particular-conditioned rye-grass. The 

 usual season of its occurrence varies a little with the earliness or 

 lateness of the grass ; it is generally encountered from the latter 

 part of June to the end of August, and is probably more fre- 

 quent in warm and dry seasons than under opposite conditions. 



Although undoubtedly in one sense a disease of the nervous 

 system, as the disturbance of innervation indicates, it does not 

 seem to originate from the nerve-centre, the cord, but from peri- 

 pheral irritation or influence consequent on the action of some 

 noxious material present in the alimentary canal. While, 

 again, there seems no doubt that the disturbance of the func- 

 tions of this nerve-centre will react in further disturbing and 

 impairing digestion, seeing that those parts or organs of the 

 animal mechanism concerned with the fulfilment of this 



