Ii80 A Manual of Veterinary Physiology. 



columns in the spinal cord ; gives origin to all the cranial 

 nerves but those of smell, sight, and the motor nerves of 

 the eyeball ; it is the head centre for the nerves governing 

 respiration, circulation, the action of the heart, and the 

 digestive apparatus from the mouth to the stomach. 



The Pons Varolii has no definite claim to be considered 

 as a nerve centre ; its use is to conduct sensory and motor 

 impressions to and fro and up and down ; it connects the 

 brain with the medulla and cerebellum ; when stimulated, 

 pain and muscular spasms are produced. Several of the 

 cranial nerves obtain connection with the grey matter of 

 the various nuclei found in it. 



The Crura Cerebri connect the cerebellum with the cere- 

 brum, and the basal ganglia with the pons and medulla. 

 They conduct both sensory and motor impulses, and are 

 connected with the complex movements of the eyeball. 

 Division of one peduncle leads to what is known as circus 

 movements, the animal travelling round and round in a 

 circle towards the opposite side to that on which the injury 

 was inflicted. 



The basal ganglia have next to be considered ; they are 

 composed of the Corpora Quadrigemina, thalami optici, and 

 corpora striata. The corpora quadrigemina are composed 

 of two parts ; an anterior and posterior pair, termed the 

 ' nates and testes.' Destruction of the corpora causes 

 blindness ; removal of one part causes circus movements or 

 rolling, or, at any rate, destruction of equilibrium and want 

 of muscular co-ordination ; not that these results are con- 

 fined to the corpora quadrigemina alone, for the same 

 inco-ordinate movements will occur on injury to the crura 

 cerebri, optic thalami, corpora striata, etc. Irritation o\ 

 the corpora quadrigemina causes contraction of the pupil, 

 whilst removal of these bodies produces dilatation. 



The Thalami Optici arc connected with vision ; but are 

 mainly supposed to be the centres for tactile impressions 

 which they transmit onwards to the cerebrum. 



The Corpora Striata are interesting clinically on account 

 of the comparative frequency with which they are diseased 



