DISEASES OF THE NEEVOUS SYSTEM 405 



From this point they proceed down the leg along with the perforans 

 tendon, and divide as in the fore-limb to supply the foot. 



The Anterior Tibial Nerve commences on the outer side of the stifle 

 joint, and dips down between the peroneus and extensor pedis muscle, 

 under cover of which it passes down the leg. On reaching the hock it 

 bears outwards, and, together with the large metatarsal artery, passes 

 down the limb to the fetlock joint, and expends itself in the skin on the 

 outer side of the os suffraginis. It gives branches to the extensor pedis 

 and flexor metatarsi, and on reaching the front of the hock some twigs 

 to the extensor brevis. 



DISEASES OF THE NERVOUS SYSTEM 



Affections of the central nervous system, including the brain and spinal 

 cord, must necessarily be of a very grave character. Physiologists allow 

 that the brain is chiefly concerned with the mental functions, but, in 

 addition, it also presides over special movements, some of which are volun- 

 tary while others are of the excito-motor character. Derangement aflecting 

 any important part or nerve centre, either in the form of excess or de- 

 ficiency of blood, undue pressure, or structural changes, produces either 

 exalted function, or drowsiness going on to stupor, or paralysis. 



Disease of the cerebellum or smaller brain causes giddiness and failure 

 of the normal power to regulate the functions of locomotion. 



The causes of cerebral derangement are numerous. As the brain pre- 

 sides over many important functions of the body, it is also sympathetically 

 affected when the organs which perform those functions become the seat of 

 structural or functional changes due to accident or disease. 



The brain is invested by certain membranes which afford protection on 

 the one hand, and on the other act as a medium through which pass the 

 vessels carrying the necessary supply of blood for the nourishment of its 

 tissues and the exercise of its function. 



CEREBRITIS AND MENINGITIS 



Very early in the history of veterinary science the French writers 

 separated diseases of the brain into two distinct forms, which were desig- 

 nated by different terms — cerebritis when the substance of the brain was 

 aff'ected, and meningitis when the inflammation attacked the membranes 

 (meninges) which cover the brain. 



The necessity for the distinction was at one time disputed, but it is 

 now quite clearly recognized; in fact, the two conditions of disease are 



