3G6 DISEASES OF THE SPINAL CORD AXD ITS MEMBRANES. 



elements, tends by pressiu'C on tliese to interfere with the due 

 performance of nervous function. 



Of the agencies which operate in the production of these 

 changes we know Httle or nothing definitely ; they may pro- 

 bably be grouped as — 1. Heredity, an ill-defined disposition to 

 develop, under certain external influences, peculiar trophic 

 changes of nervous matter. 2. Overwork and exhaustion, 

 particularly when combined with exposure to adverse climatic 

 influences. 3. It may follow as a sequel of other diseased 

 stat'es, as certain fevers, or inflammatory action involving the 

 particular localities of the nervous centres, afterwards exhibiting 

 the sclerous changes. 



Anatomical Characters. — The more obvious appearance of 

 disease in nervous sclerosis is the occurrence of greyish 

 patches or circumscribed tracts of varying extent; I have 

 noticed them in greatest amount in connection with the 

 lateral lobes of the cerebellum in the horse — in some they 

 appear as enlargements of the entire tissue affected, in others 

 no alteration in bulk or form is appreciable. They are of 

 varying degrees of toughness, firmness, or hardness, exhibiting, 

 where incised, many of the characters of common fibrous 

 tissue. Over the outer surface of these patches the pia 

 mater is often firmly adherent. 



Examined more minutely, the extra development of the 

 ordinary connecting tissue seems to have separated the nerve- 

 tubes, which in well-marked instances appear pressed upon 

 and shrunk, the true myeline matter being in diminished 

 quantity, while in the grey matter the cell-elements show 

 deviation from the normal character. 



Symptoms. — These in all cases depend upon the locality of 

 the sclerous changes. I have observed that they to a greater 

 extent include disturbance of motor than of sensory power, 

 although both are ultimately afl'ected. Rarely does paral3'sis 

 in any form suddenly show itself, rather is the aberration a loss 

 of co-ordination of movement of the muscles of the limbs. 

 When the sclerosis existed in the cerebellum the animals 

 showed a disposition particularly to gyration in movement, Avith 

 spasmodic action of the muscles of the eye-ball. All these dis- 

 turbances of nervous function are, in cases of sclerosis of tlie 

 spinal cord, apt to be complicated, rarely rapidly culminating 



