1896.J MICROSCOPICAL JOURNAL 415 



lung-breathing vertebrate this region is relatively smaller 

 and in the mammalia it is se])aratc'd from the mouth by 

 the soft palate and the muscular pillars of the fauces, 

 as thrt phiri/ai;. lu the hig'.ier forms dariu^i^ thair em!)ryoaic 

 or larval life the throat and circulation are distinctly 

 piscine. 



7. The Brain. — Cut away the mouth walls and floor 

 and ])in the upper 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 while nervous tissues; beneath the 

 bones you will find masses of cartilage surrounding the 

 brain, pare these away as much as possible without dam- 

 aging the brain. Explore the ]»arts of the brain with a 

 fine probe without dislocating them. The two largest 

 rounded lobes of the brain are the optic lobes, directly 

 in front of them are two smaller rounded masses, the 

 cerebral he mispheres', 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 C'jiW be seen running from the nose c'lamber 

 to the olfactory lobes on either side by the help of a 

 little dissection. The optic nerve can also be traced to 

 the oi)tic lobes which they enter on their ventral as[)ect. 

 Other 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 

 demonstrate its direct relation with themedulla oblongata. 

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

 the head in two in the mid lie line an I locate the brain in 

 relation to the head in the side view and draw. 



