1 6 Veterinary Medicine. 



pons. This is excited by excess of carbon dioxide in tlie blood, 

 by suffocation, drowning, by anaemia of the bulb from bleeding 

 or ligature of the carotids, by venous congestion after ligature of 

 the jugulars, or by the direct application to the part of ammonia 

 carbonate, or salts of potash or soda. It may also be aroused by 

 afferent nervous currents from different peripheral parts (spinal 

 cord, sciatic nerve, etc. ) . 



A Perspiratory Centre is found in the medulla, on each side, 

 which may be roused into action by diaphoretics (opium, ipeca- 

 cuan, tartar emetic. Calabar bean, nicotin, picrotoxin, camphor, 

 pilocarpin, ammonia acetate, etc.). 



The Pons like the medulla is at once a ganglionic and con- 

 ducting organ, and its lesions may lead to arrest of nerve currents 

 generated above or below it, or to the failure to develop currents 

 in its, own centres. Stimulation of its superficial layers may be 

 without effect, but if this is carried into the centre epileptiform 

 convulsions ensue. I,esions of one side of its posterior half cause 

 facial paralysis the same side and motor and sensory paralysis on 

 the opposite side of the body (crossed hemiplegia) . Lesions of one 

 side of its anterior half cause paralysis in both face and body on 

 the same side. This depends on the crossing of the fibres mid- 

 way back in the pons, which cross again in the medulla (motor 

 fibres) and in the spinal cord (sensory fibres). lycsions of the 

 pons are liable to interfere with the functions of the trigemini, 

 the oculo motor and the superior oplique, and to determine 

 epileptic movements and loss of coordination of sensorio-motor 

 movements. I,esions of the superficial transverse fibres (median 

 cerebellar peduncles) tend to cause involuntary movements to 

 one side. 



Lesions of the Corpora Quadrigemina cause disturbance of 

 vision, failure of the pupil to contract to light, blindness, paralysis 

 of the oculo-motor nerves, and lack of coordination of move- 

 ments. Stimulation of one anterior corpus causes rolling of 

 both eyes to the opposite side, with, if continued, a similar move- 

 ment of the head and even of the body (horse in mill, or index 

 motion, or rolling on its axis). 



The Crura Cerebri are conducting bodies but contain also 

 different nerve centres. Lesions of one crus cause violent pain 

 and spasm on the opposite side of the body, followed by paralysis. 



