VIII.] THE COMMON FROG. 117 



from the swollen head of each proceed the delicate 

 nerves of smell. 



2. An enormous pair of folded masses, which form 

 the great bulk of the human brain, and are called the 

 cerebral lobes or hemispheres. These are so large and 

 preponderant in man, as to hide every other part of 

 the human brain when that organ is viewed from 

 above. 



3. A relatively very small portion, but one easily 

 recognized, since it supports two conspicuous little 

 bodies. One of these (Figs. 69, 70, 71, pi) is called 

 t\\Q pineal glajid, and projects more or less upwards; 

 the other (Figs. 69, 70, 71, pt) projects downwards, 

 and is called the pituitary body. 



4. An also very sm.all portion relatively, is distin- 

 guished by bearing certain small prominences (Fig. 

 69, cq, and Fig. 70, na and te) placed behind the pineal 

 gland and called coipora quadrigeuiina. 



5. A rounded mass of finely-folded brain-substance, 

 placed at the lower part of the back of the head, 

 beneath the hinder portion of the cerebral hemi- 

 spheres. This is called the cerebelhim, and when cut 

 through exhibits singular, radiating, tree-like mark- 

 ings, due to the infoldings of the surface of the organ, 

 and called the arbor vitcB (Fig. 70, av). 



6. That part which directly continues the brain 

 into the spinal marrow (Fig, 71, in). It is overlapped 

 by the cerebellum, and contains that portion of the 

 remnant of the primitive nervous canal, which is 

 named \h^ fourth ventricle. This sixth fundamental 

 part of man's brain is called the mednlla oblongata. 



On turning to the brain of the frog from that of 



