THE CEREBRAL HEMISPHERES. 319 



which converge to the gray substance of the corpora otriata. 

 The fibres from the middle portion converge regularly to the 

 middle region of the external portions of the optic thalami. 

 The fibres from the posterior portion pass from behind for- 

 ward, and distribute themselves in the posterior portion of 

 the optic thalami. The fibres from the convolutions of the 

 hippocampi and the fascia dentata are lost in the gray sub- 

 stance lining the internal borders of the optic thalami. In 

 addition to these converging fibres and the curved commis- 

 sural fibres connecting the different convolutions of each 

 hemisphere with each other, are commissural fibres which 

 connect the two hemispheres, as well as fibres connecting 

 together the corpora striata and the optic thalami of the 

 two sides. 



Certain of the fibres converging from the gray substance 

 of the hemispheres to the corpora striata and optic thalami 

 are probably connected with the cells in the gray matter of 

 these parts. Other fibres pass through the corpora striata 

 and optic thalami to become finally connected with the 

 fibres of the medulla oblongata, and, through the medulla 

 pblongata, with the columns of the spinal cord. Following 

 the antero-lateral columns of the cord from below upward, 

 they ascend to the medulla oblongata, decussate in the me- 

 dian line, and from the medulla pass to the brain. Certain 

 of these ascending fibres, which are nearly all continuations 

 of the antero-lateral columns of the cord, ascend to the brain 

 by passing deeply through the pons Yarolii ; other fibres as- 

 cend in the cerebral peduncles, or crura cerebri ; and other 

 fibres pass to the tubercula quadrigemina. As the bundles 

 of fibres ascend from the medulla oblongata, they become 

 more and more numerous by reinforcements of fibres, proba- 

 bly derived from the cells of the collections of gray matter in 

 their course. 



"We have attempted, in the above sketch of the fibres of 

 the brain, to give a succinct account of the points that are 

 most interesting from their physiological relations, and to' 



121 



