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, 



C.TA' 



c.rs. 



v.vn. 



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 ; 011 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 

 iiiterpositum and pineal body are removed, as well as the greater part of the body of the fomix, 

 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 ; 

 <(. pn. anterior peduncles of cerebellum; b. fo. body of fornix; dA. superior vermis of cere- 

 bellum ; c'A 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 ; 

 (/. p. dorsal pyramid ; fl. flocculus ; hp. m. hippocampus major ; m. co. middle commissure ; 

 o. P. anterior ; o. 1%. posterior lobes of corpora quadrigemina ; o. t/i. optic thalamus ; o. tr. optic 

 tract ; p. co. posterior commissure ; p. fo. posterior pillar of fornix ; pn. pineal body ; p<L p,t. 

 peduncle of pineal body ; p. pn. posterior peduncles of cerebellum ; p. ra. fibres of pons 

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

 tudinalis ; t. .s. tojnia semicircularis ; r. r/i. valve of Vieussens ; r3. third ventricle ; r4, 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 



