348 ANATOMY OF THE RABBIT 



if it is removed en masse the paraflocculus 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 if the anterior portion of the cord has not already 

 been exposed in the previous dissection. 



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

 third vertebrae. The brain should then be raised very gently 

 from the ventral wall of the skull and the nerve roots should be 

 divided with fine, sharp scissors. This operation requires con- 

 siderable care not to pull upon the nerves since these are strongly 

 attached at their points of exit from the skull but very lightly 

 attached to the brain, so that they are in danger of being torn 

 away from the latter. 



The anterior end of the brain may be freed by cutting close to 

 the bone under and in front of the small anterior expansions 

 formed by the olfactory bulbs. 



The dura mater is adherent to the inner surface of the 

 cranium but may be stripped away from it in the process of 

 removal of the bone. Portions which remain attached to the 

 brain may be cut away with scissors. Such attachment will be 

 found chiefly along two lines: one, where the membrane extends 

 down into the longitudinal fissure between the cerebral hemis- 

 pheres, as the falx cerebri, the other the tentorium cerebelli, a 

 transverse fold extending inward between the cerebral hemis- 

 pheres and the cerebellum. These parts contain wide vessels 

 which receive most of the blood from the brain, the superior 

 sagittal and the transverse venous sinuses, from the latter of 

 which the blood passes into the superficial temporal vein (p. 297). 

 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. 



4. The primary divisions of the brain are explained in a previous 

 chapter (p. 80). The prosencephalon or forebrain, the mesen- 

 cephalon or midbrain, and the rhombencephalon or hindbrain, 

 though much elaborated in form, are still to be recognized in 

 the adult animal. Their superficial features may be identified 

 as follows: 



