578 PONS VAROLII. 



— The corpus restiforme, has been traced backwards into the 

 clneritious coating of the cerebellum, and there is much reason to 

 consider that its fibres form a doubling or reflection there, and 

 again come forwards as a part of the pons varolii. The other 

 three columns we can trace upwards through the anterior part of 

 the pons varolii, and crura cerebri, to the brain. 



Pons Varolii. 



— By dividing on the lower surface of the pons the transverse 

 fibres which come from the cerebellum to the depth of about 

 one-eighth of an inch on the middle line, and then scraping 

 them back towards the cerebellum, the fibres of the corpus 

 pyramidale will be seen advancing through the pons varolii, 

 emerging from the anterior or upper edge of this body, transvers- 

 ing the upper part of the crus cerebri, a part of the thalamus 

 opticus, and finally expanding into the corpus striatum g, to 

 concur in the formation of the lobes of the cerebrum. The 

 divergence of the two crura cerebri, forms the posterior bounda- 

 ries of the lozenge-shaped cavity of the base of the brain. The 

 fibres of the corpus pyramidale are separated from each other in 

 their course through the pons, by gray matter, and the fasciculus ap- 

 pears in consequence to increase in its breadth. According to 

 Tiedemann, the transverse fibres of the pons, forming what 



fibres of the anterior column, from the corpus pyramidale, which begin to 

 diverge and to be reinforced. 



On the left side, the brain being inverted, is seen a vertical section of the 

 cerebellum, made through the entrance into it of the corpus restiforme m, (Pos- 

 terior column of the spinal marrow.) w. Corpus dentatum or ganglion of the 

 cerebellum, showing the augmentation of the corpus restiforme in the ganglion, 

 and from which the medullary branches and twigs divide to the leaflets of the 

 cerebellum. The whole of this medullary arrangement, constitutes the arbor 

 vitffi. 0, Nervous fibres cut ofi", whicli spread out from the thalamus into the 

 convolutions of the middle lobe, p, Medullary fibres which pass through the 

 corpus striatum, reinforced as they proceed to the anterior lobe. The middle 

 lobe of the brain on this side is entirely removed, which exposes the side of the 

 ^reat lateral ventricle, q. In front of it a small section of the anterior lobe is 

 seen, and the fibres which radiate into that lobe from the thalamus and corpus 

 striatum. E, Inner termination of the fissure of Sylvius, from which the 

 middle lobe has been cut, showing its proximity to the corpus striatum in the 

 central part of the brain. 5, Fourth pair of nerves, i t, Anterior lobe of the 

 cerebrum, u, Middle lobe, v, Posterior lobe. On the right side, just below the 

 corpus olivare, are seen the arciform fibres of Santorini. In front of e is seen 

 the auditory and facial nerves. 



