272 Anatomy of the Rabbit. 



lateral wall of the skull on both sides. The chief part of the 

 operation consists in removing the temporal portion of the skull 

 by successive steps, exposing first the flocculus of the cerebellum, 

 a small stalked body which is almost completely enclosed by the 

 dorsal portion of the petrosal. The entire petrotympanic bone 

 is easily detached, and if removed en masse the flocculus and 

 probably also the roots of the facial and acoustic nerves will be 

 destroyed. 



The arches of the first three or four cervical vertebrae should be 

 removed, unless the anterior portion of the cord, has been exposed 

 in the previous dissection. 



The spinal cord, may be divided at about the level of the third 

 vertebra. The brain should, then be raised very gently from the 

 ventral wall of the skull and the nerve roots divided with a small 

 sharp knife or with fine scissors. This operation requires con- 

 siderable care, since the nerves are strongly attached, at their points 

 of exit from the cranial wall, but very lightly attached to the brain, 

 so that they are in danger of being torn away. 



The anterior end. of the brain may be freed by cutting across the 

 small anterior expansions formed by the olfactory bulbs. 



Portions of the dura mater removed with the brain may be cut 

 away with scissors. It is adherent chiefly along two lines: one 

 representing the longitudinal fissure between the cerebral hemi- 

 spheres, the other the tentorium cerebelli. These parts contain the 

 superior sagittal and transverse venous sinuses. 



On the ventral surface of the brain as removed, appear the 

 basilar and internal carotid arteries and their branches. These 

 vessels should be kept intact for examination at a later stage. 



For the primary divisions of the brain see p. 71. 



4. The superficial features may be identified, as follows: 



IX THE PROSENCEPHALON : 



(a) The greatly enlarged, cerebral hemisphere i hemisphaerium 

 cerebri) forms with its fellow of the opposite side the largest 

 portion of the brain. The two structures are separated by 

 the longitudinal cerebral fissure, but are connected with 

 one another by the commissures indicated below. 



(b) The olfactory bulb (bulbus olfaetorius) is a small ex- 

 pansion King at the anterior end of each hemisphere. Its 



