THE NERVOUS SYSTEM. 387 



tracts, bofh in the majority of nerves and in the spinal 

 cord. Tlie degree of palsy may vary from that of a 

 single muscle to total paralysis. When the whole of one 

 side of the body is affected, it is termed hemiplegia, 

 when both hind limbs, paraplegia. In the other cases, 

 simply " paralysis.'^ It may result from pressure on, or 

 disease of the medulla oblongata, pressure on the 

 spinal cord on the same side as the loss of power 

 between the origin of the roots of the nerves and the 

 brain, or on the nerves of supply to the affected part. 

 Section of these structures or diseased action has the 

 same effect. The loss of power does not generally occur 

 suddenly, though it may do so, but where the limbs are 

 affected there is a staggering gait, and a tendency to cross 

 the hind legs. The most prevalent form in the ox is 

 paraplegia. It is most frequent in old animals, especially 

 those turned out on damp low pastures and during severe 

 weather. All hardships tend to the occurrence of cases 

 of this kind in the herd. Sometimes we find that 

 the pressure on the nerves or cord is due to fracture ; 

 in this case the paraplegia occurs suddenly after a fall 

 or some other form of injury, and the animal retains 

 sensibility and motor power in all parts anterior to the 

 fracture, and loses them posteriorly, but it must be 

 remembered that reflex movements may occur, though 

 they are not frequent. In the horse, intermittent para- 

 lysis of the hind limbs has been found to be due to 

 plugging of the iliac arteries with lymph ; such cases 

 have not been noticed in the ox, but cases of paraplegia 

 in pregnant animals are sometimes seen, in which the 

 paralysis disappears after parturition ; in them there may 

 be pressure on the posterior aorta, or the iliacs more 

 particularly, interfering with blood supply. Tumours of 

 various kinds may be observed post-mortem, or even 

 during life, in such positions as to press upon the nerves 

 of the affected part. Sometimes paralysis is due to the 

 action of poisonous agents ; of these cases, lead palsy is 

 the most remarkable. 



Treatment. — All attention must be paid to the comfort 



