110 



NON-SPECIFIC OR GENERAL DISEASES 



they terminate in a small, central canal. The isthmus is the 

 highway between the spinal cord and the higher nerve centres. 

 It has in it certain cell centres that give origin to six of the 

 cranial nerves. 



The third division of the brain is the cerehellum. This is a 

 single mass supported by the isthmus. It is situated posterior 

 to the cerebrum, from which it is separated by a transverse fold 



Fio. 25. — Photograph of model of horse's brain : (D) longitudinal section; (E) lateral 

 view; (A) cerebrum; (B) cerebellum; and (C) isthmus. 



of the membranes covering the brain. This mass of nerve tissue 

 is much smaller than the cerebrum. The white neiwe tissue 

 forms central nuclei which send out branches that ramify in every 

 direction. The centre of the muscular sense is said to be located 

 in this division of the brain. A second function is the mainten- 

 ance of body equilibrium through its connection with the nerve 

 of the middle ear. 



The spinal cord commences at the posterior opening (occipi- 



