THE NERVOUS SYSTEM 



hemispheres are smaller and fail to hide the cerebellum and medulla oblongata 

 (Fig. 82). The cerebral hemispheres, which are separated by a deep cleft called 

 the longitudinal fissure of the cerebrum, together present a broad convex surface 

 which lies in close relation to the internal aspect of the calvaria. From the 

 latter it is separated only by the investing membranes or meninges of the brain. 

 The thin convoluted layer of gray matter upon the surface of the hemispheres is 

 known as the cerebral cortex. 



The ventral aspect or base of the brain presents an irregular surface adapted 

 to the uneven floor of the cranial cavity (Figs. 83, 86). The medulla oblongata, 



Face and tongue 



Head and eyes 



Fore limb 



Hind limb 



Gyrus sylviactis (arcuatus) 



Cyrus lateralis 

 Gvri mediates 



Gyrus internus I / /- 



Vermis cerebelli 

 Hemisptuerium cerebelli 



Medulla oblongata 

 Medulla spinalis 



Gyrus frontalis medialis 

 Gyrus frontalis superior 

 Sulcus coronal is 

 Sulcus splenialis 

 Fissura ansata (cruciata) 

 Fissura lateralis (Sylvii) 



Fissura suprasylvia 

 Fissura longitudinalis 

 Sulcus lateralis 

 Sulcus intermedius 

 Sulcus medialis 



Flocculus 



Neruus accessorius 

 Nervus spinalis I 



Fig. 82. Dorsal view of the sheep's brain. The motor cortex is shaded on the left side. (Herrick 



and Crosby.) 



which is continuous through the foramen magnum with the spinal cord, lies on 

 the ventral aspect of the cerebellum in the vallecula between the two cere- 

 bellar hemispheres. Rostral to the medulla oblongata and separated from it 

 only by a transverse groove is a broad elevated band of fibers, which plunges 

 into the cerebellum on either side and is known as the pons. The cerebellum 

 can be seen occupying a position dorsal to the pons and medulla oblongata, and 

 can easily be recognized by its grayish color and many parallel fissures. A 

 pair of large rope-like strands are seen to emerge from the rostral border of 

 the pons and to diverge from each other as they run toward the under surface 



