340 



NERVOUS SYSTEM. 



In the following account of the brain of the cat all parts 

 will be described as far as possible in relation with the tubular 

 structure of the brain. The brain will be considered as a 

 hollow structure, having central cavities, and the solid portions 

 will be brought into relation as parts of the roof, sides, or floor 

 of the cavities. The cavities of the brain, forming a direct 

 continuation of the central canal of the spinal cord, are known 

 as ventricles (ventriculi). 



In a general view of the cat's brain from the dorsal side 

 (Fig. 137) four subdivisions are discernible. At the caudal 



- -m 



FIG. 137. DORSAL SURFACE OF THE BRAIN. 



/, olfactory bulbs; //, cerebral hemispheres; ///, cerebellum; IV, medulla, a, 

 prsesylvian sulcus; b, cruciate sulcus; c. sulcus ansatus; d, coronal sulcus; e, anterior 

 sulcus; /, posterior sulcus; g, suprasylvian sulcus; h, separate parts of the lateral 

 sulcus; i, end of splenial sulcus;/, vermis of cerebellum; k, hemispheres of cerebel- 

 lum; /, roof of fourth ventricle ; ;, first cervical nerve. I. orbital lobe (or gyrus); 

 2. sigmoid gyrus; 3, anterior sylvian gyrus; 4. ectosylvian gyrus; 5, suprasylvian 

 gyrus; 6, posterior sylvian gyrus; 7, parts of marginal gyrus; 8, gyrus compositus 

 posterior. 



end is a small stalk-like portion (IV) which is clearly a slightly 

 modified continuation of the spinal cord ; this is the myelen- 

 cephalon or medulla oblongata. Just craniad of this, rising 



