138 THE COMMON COLICS OF THE HORSE 



febrile disturbance), how that the accumulated lumps of 

 faecal matter become so hardened by the withdrawal of 

 moisture as to seriously prejudice their chance of effectual 

 displacement by normal intestinal movements. 



Also, regarding this portion of the intestinal tract, 

 some little attention should be paid to the consideration 

 of nervous trouble as a primary cause. I do not wish 

 the reader to imagine anything obscure in its nature or 

 of comparatively rare occurrence. It is something quite 

 simple to understand, and of more or less every-day 

 happening. Everyone is aware of the fact that a nerve 

 is paralyzed — its function temporarily inhibited — by being 

 in contact with an overworked or tired muscle, a muscle 

 that is impregnated with effete materials that its long 

 continuing work has left it too fatigued to rid itself of. 

 It may be, perhaps out of sympathy, perhaps by a 

 process of absorption whereby it takes up a certain 

 amount of the poisonous muscle waste, that nerves or 

 nerve-centres in close apposition with such overworked 

 muscles become paralyzed, and fail temporarily to per- 

 form their proper function. 



In this manner the posterior mesenteric plexus (formed 

 in great part by the lumbar portion of the great sym- 

 pathetic system, and furnishing branches for the supply 

 of the small colon and the rectum) may often be so 

 induced to a state of dangerous lethargy. The lumbar 

 portion of the sympathetic, lying as it does in close con- 

 tact with the psoas muscles, and being largely covered by 

 the posterior vena cava, would be almost the first nerve- 

 centre supplying the intestinal tract to feel the ill effects 

 of the waste materials from the muscles of the hind 

 limbs and the loins. At any rate, whatever the explana- 

 tion may be, it is certain that prolonged and excessive 

 work, especially that of a heavy hauling nature, telling 



