ANATOiriCAL STRUCTURE OF THE SHEEP. 109 



They arise by numerous filaments from both the superior 

 and inferior surface? of the spinal cord, the filaments intertwine, 

 and before they emerge through the dura mater, they join to- 

 gether just anterior to their union, a sort of knot being formed 

 on the upper nerve, which is termed a ganglion. This upper 

 nerve is the one conveying sensation, while the lower is the nerve 

 of motion, so these nerves, originating as they do, form different 

 portions of the spinal cord, even after they join together. The 

 intimate fibres convey, or rather own, different attributes, al- 

 though all are bound together in one sheath. Lastly we shall 

 mention the sympathetic nerve, it rivalling in importance the 

 pneumogastric, ■which has already been described. 



The great sympathetic nerve ' is the nervous apparatus 

 of the organs of vegetative life. It extends in the form of two 

 long cords from the head to the tail, the two cords being situated 

 immediately under the vertebral column to the tail, appearing 

 to arise from a ganglion at the base of the brain, anterior to the 

 commencement of the spinal cord. By its numerous branches 

 it is connected vpith all the other nerves, and distributes branches 

 to all the glands, blood vessels and lymphatics of the system, 

 also the heart, lungs, and digestive organs. It is the virtual life 

 of the organic system, influencing all functions of nutrition and 

 secretion. 



The brain of the sheep is small when compared with that 

 of other animals, the whole make-up of its nervous system being 

 comparatively feebly developed. This fact has a considerable 

 influence over the diseases which affect the animal, accounting 

 for the fact that in so many debility quickly follows sickness; 

 the sheep speedily succumbing to what at first appear to be 

 slight ailments. 



