420 ANATOMY AND PHYSIOLOGY OF THE BRAIN. 



The ascending are those of the pillars of the brain, which, 

 coming from the anterior pyramids, lateral columns, and 

 posterior pyramids, acquire additional fibres in passing 

 through the pons Varolii, optic thalami, and corpora striata, 

 and from the latter diverge into all parts of the hemi- 

 spheres. Fibres of a similar kind are derived from the 

 anterior peduncles of the cerebellum, the corpora quadri- 

 gemina, and the corpora geniculata. 



The transverse fibres pass between the two sides of the 

 brain, and are collected in great part into the corpus callo- 

 sum. The white bands which connect the corpora striata 

 and the optic thalami belong to the same order. 



The longitudinal fibres are represented in great part by 

 the fornix, the fibres of which, passing from the optic 

 thalami, join the corpus albicans, whence they turn upward 

 and backward in the median line, and ultimately bend 

 down to become connected on each side with the hippo- 

 campus major and fimbriated body. At its posterior part 

 it is connected with the pineal body. A layer of longi- 

 tudinal fibres on the upper aspect of the corpus callosum, 

 and several other smaller bundles of the same kind, likewise 

 belong to this class. 



The oblong medulla performs functions similar to those 

 of the spinal cord as a conductor of nervous force. These 

 are more important, however, as it will be seen from its 

 position that all truly sensory impressions from parts sup- 

 plied by spinal nerves must traverse the medulla in their 

 course toward the sensorium, and in all voluntary move- 

 ments of such parts the motor impulse must pass through 

 its substance to gain the nerves of innervation. The same 

 may be said of all reflex motor power originating in the 

 medulla itself. 



As a nervous centre this portion of the brain likewise 



