1896.] MICROSCOPICAL JOURNAL 415 



lung-breathing vertebrate this region is relatively smaller 

 and in the mammalia it is separated from the moutii by 

 the soft palate and the muscular jjillars of the f;iuct*s, 

 as the phiiri/fix. hi tli3 hig'irtr forms dariuj^ thiir en'iryo lic 

 or larval life the throat and circulation are disiinctly 

 piscine. 



7. The Brain. — Cut awa;y the mouth walls and floor 

 and pin the up{)er part of the head down under water, 

 dissect away the skin and muscles from the cranium and 

 cut away the bones covering the brain, be very careful 

 not to injure the soft white 7iervoiis tissues; beneath the 

 bones you will find masses of cartilage suiTOunding the 

 brain, pare these away as much as [)Ossible without dam- 

 aging the brain. Explore the parts of the brain with a 

 fine probe without dislocating them. The two birgeat 

 rounded lol)es of the brain are the optic lobes, directly 

 in front of them are two smaller rounded masses, the 

 cerebral he /nispheres; the olfactory lobes are partly separ- 

 ate, lobed anterior portions of the cerebral hemispheres, 

 in some cases they seem almost separate structures. The 

 olfactory nerve ctin be seen running from the nose c'lamber 

 to the olfactory lobes on either si<ie by the help of a 

 little dissection. The optic nerve can also be traced to 

 the optic lobes which they enter on their ventral aspect. 

 Oilier cranial nerves may possibly be seen. The portion 

 of the brain behind the optic lobes presents two chief 

 parts: a dorsal median rounded cerebellum; and ventrally 

 to this the medulla oblongata. These lie in the extreme 

 posterior portion of the cranium. Follow the nervous 

 tissue back into the trunk region, note that it is enclosed 

 in a passage, spinal canal, in the back-bone. Cut away 

 bone enough to give you a view of the spinal cord and 

 dt^inonstrate its direct relation with tiie medulla oblongata. 

 Draw a view of the brain in position in the head. Split 

 the head in two in the raid.lle line an I locate the bruin iu 

 relation to the head in the side view and draw. 



