440 



ZOOLOGY 



SECT. 



from the rest. There are very large club-shaped olfactory lobes at 

 the anterior extremities of the cerebral hemispheres. Connecting 

 together the two hemispheres is a commissural structure the 

 corpus callosum (Figs. 1032, 1033, cp. cl.) not present in the Pigeon ; 

 this runs transversely above the level of the lateral ventricles. 

 Examined in transverse section, i.e., in a longitudinal section of the 

 brain (Fig. 1033), the corpus callosum is seen to bend downwards, 



olf 



FIG. 1032. Lepus cuniculus. Two dissections of the brain from above (nat. size.) In A the 

 left parencephalon is dissected down to the level of the corpus callosum ; on the right the 

 lateral ventricle is exposed. In B the cerebral hemispheres are dissected to a little below 

 the level of the anterior genu of the corpus callosum ; only the frontal lobe of the left 

 hemisphere is retained ; of the right a portion of the temporal lobe also is left ; the velum 

 interpositum and pineal body are removed, as well as the greater part of the body of the fornix,. 

 and the whole of the left posterior pillar ; the cerebellum is removed with the exception of a 

 part of its right lateral lobe. a. co. anterior commissure ; a. fo. anterior pillar of fornix ; 

 a. pn. anterior peduncles of cerebellum ; &. fo. body of fornix ; cbi. superior vermis of cere- 

 bellum ; <*2. its lateral lobe ; c. gn. corpus geniculatum ; c. h. cerebral hemisphere ; ch. pi. 

 choroid plexus ; cp. cl. corpus callosum ; cp. s. corpus striatum ; c. rs. corpus restiforme ; 

 d. p. dorsal pyramid ; fl. flocculus ; hp. m. hippocampus m'ajor ; m. co. middle commissure ; 

 o. 11. anterior ; o. P. posterior lobes of corpora quadrigemina ; o. th. optic thalamus ; o. tr. optic 

 tract ; p. co. posterior commissure ; p. fo. posterior pillar of fornix ; pn. pineal body ; pd. pn. 

 peduncle of pineal body ; p. pn. posterior peduncles of cerebellum ; p. i-a. fibres of pons 

 Varolii forming middle peduncles of cerebellum ; sp. lu. septum lucidum ; st. I. stria longi- 

 tudinalis ; t. s. toenia semicircularis ; v. vn. valve of Vieussens ; r3. .third ventricle ; v4, fourth 

 ventricle. (From Parker's Zootomy.) 



forming what is termed the genu ; posteriorly it bends downwards, 

 forming the splenium, which passes forwards and is united with the 

 fornix. Below the corpus callosum is another characteristic struc- 

 ture of a commissural nature the fornix (b.fo.) a narrow median 

 strand of longitudinal fibres, which bifurcates both anteriorly and 

 posteriorly to form the so-called pillars of the fornix (anterior and 

 posterior) (a.fo., p.fo.). Below the corpus callosum, between it 

 and the fornix, the thin inner walls of the hemispheres (septum 



