336 Journal of Comparative Neurology. 



the cerebellum often offers great difficulties to orientation. 

 If the brain be approached from above, by a cautious paring 

 down of the head in the horizontal plane until the cavity of 

 the skull is reached, the opening may be gradually enlarged 

 by strong shears and the forceps, snipping away carefully 

 with sharp scissors the membranous adhesions. The olfac- 

 tories, if included, give comparatively little trouble, but, if 

 excluded, not a little skill is required to isolate the crura and 

 dislodge the bulbus. The principal objection to this method 

 is the difficulty of satisfactorily dissecting out the stumps of 

 the cranial nerves. In many cases we have found it safest to 

 remove the whole mass of fat containing the brain and pass 

 it through the solutions unaltered. In this case the solution 

 of the fats in the alcohol leaves cavities which become filled 

 with vapor and are permeated with extreme slowness by the 

 imbedding media. When they are imperfectly filled there is 

 little hope of securing a consecutive series of sections. 



It is advisable to remove some of the brains from below, 

 in which case the jaw is carefully cut (not torn) away, 

 taking pains not to bring to bear any tension on the nerves in 

 the process. The opercular apparatus is then removed and 

 the region of the eighth nerve is easily located by the appear- 

 ance of the otolith sac. The opening is extended with the 

 shears, with the precaution of cutting each nerve fibre within 

 the cranial cavity before the corresponding area is removed. 

 The saccus vasculosus and hypophysis are then isolated, and 

 all the fibrous connections of one side are removed. The 

 whole lower part of the head is cut away piece-meal until 

 the nerve roots of the other side are reached. The cord is 

 then severed, and, as the nerves are cut the brain is gently 

 pushed laterad and allowed to drop into the fixing bath, 

 without first removing the fatty envelopes. 



Pixinij^. — While it is desirable that a fish brain shall be 

 perfectly fresh, the importance of having it absolutely alive 

 has been exaggerated. The supposed necessity of plunging 

 it at once into absolute alcohol will account for many of the 



