ix.] THE NERVOUS SYSTEM. 367 



the corpus callosum} which extends much nearer to the an- 

 terior than to the posterior end of the longitudinal fissure. 

 In front of the corpus callosum is seen nothing but the 

 anterior fossa of the cranial cavity ; but behind the corpus 

 callosum (after removing that fold of the dura mater, the 

 tentorium so often ossified in brutes which extends in from 

 behind, below the cerebrum) we find the upper surface of 

 another part of the cerebro-spinal axis, called the cerebellum, 

 which is marked with numerous transverse, close, narrow 

 grooves. To remove the entire brain from the skull it is 

 necessary to cut through that part of the cerebro-spinal axis 

 where the brain (at the foramen magnum) becomes con- 

 tinuous with the spinal marrow. 



5. Having done this, and inverted the organ, a variety of 

 parts come into view, its INFERIOR SURFACE being very 

 irregular and complex as compared with its superior surface. 



Proceeding from behind forwards, we find that the part in 

 front of the section which we have just made is narrow and 

 cylindrical. This is the medulla oblongata. It is marked by 

 a median groove, on each side of which is what is called 

 the anterior pyramid, and outside each such pyramid is a 

 rounded, oblong prominence, termed the olivary body ; and 

 external to and behind each of these is a band named the 

 restiform tract. The cut surface of the medulla exhibits that 

 double-crescentic arrangement of grey tissue described in the 

 "Elementary Physiology," Lesson XI. 5. 



On each side of the medulla oblongata is seen a large con- 

 vex mass of tissue marked with many curved, transverse, 

 narrow grooves. This is the cerebellum . and its two lateral 

 parts meet together behind the medulla and form what is 

 called the inferior vermis. This latter is the under part of 

 that median portion of the cerebellum which we saw by 

 divaricating the hinder parts of the cerebral hemispheres 

 and which is called the superior vermis (Fig. 328, sv). The 

 median part of the cerebellum is small compared with its 

 two great lateral lobes. 



The cerebellum lies in that fossa of the cranial cavity 

 which we have seen to be bounded in front by the petrous 

 part of the temporal bones, and behind by the line of attach- 

 ment of the tentorium to the occipital bone. 



On each side of the anterior part of the under surface of 

 the cerebellum is a small process, or lobe, called \heflocculus. 

 It does not occupy any special fossa in the temporal bone. 



Continuing on in the middle line, we find in front of the 



