FIBRES OF THE CEREBRUM 



579 



remembered ; but there are distinct evidences of the perception of pain, 

 even when the cerebrum has been removed. 



Directions of the Fibres in the Cerebrum. Fibres pass from the 

 cerebral hemispheres to the cerebellum. Commissural fibres connect 

 the cerebrum and certain of the basal ganglia on the two sides. Fibres 

 connect the gray matter of cerebral convolutions on the same side. 

 Fibres pass from the inner surface of the gray matter of the cerebrum 

 to the internal capsule, corpora striata, optic thalami and pons Varolii, 

 the bulb and thence to the spinal cord. The directions of these four 

 sets of fibres have been quite accurately described. 



1. Fibres connecting the Cerebrum with the Cerebellum. (A) Fibres 

 from the gray matter of the frontal lobe, in front of the anterior central 

 convolution, pass through the anterior division of the internal capsule 

 and thence through the inner portion of the outer layer of the crus 

 cerebri (crusta) to the pons, where they seem to go to the cells of the 

 gray matter, forming synapses. From the pons, fibres go to the lateral 

 and posterior regions of the cerebellum on the opposite side. (B) Fibres 

 from the occipital and temporo-sphenoidal lobes pass in the outer portion 

 of the crusta and go to the upper portion of the cerebellum, near the 

 middle lobe. This connection probably is crossed. (C) Above the 

 pyramidal tract of the crusta, is a small tract of fibres which connects 

 the caudate nucleus of the corpus striatum, through synapses in the 

 pons, with the cerebellum on the opposite side ( Cowers). 



2. Fibres connecting the Two Sides of the Brain. (A) Fibres 

 from the inner surface of the gray matter of the convolutions pass from 

 one side to the other, through the corpus callosum, and connect the two 

 hemispheres. These are the transverse fibres of the corpus callosum. 

 (B) Fibres from the gray matter of the temporo-sphenoidal lobes pass 

 through the corpora striata to the anterior commissure. These connect 

 the temporo-sphenoidal lobes, and probably the corpora striata, on the 

 two sides. (C) Fibres from the deeper portion of the crus cerebri 

 (tegmentum) pass to the optic thalamus on either side and thence to the 

 temporo-sphenoidal lobes. They form the posterior commissure and con- 

 nect the temporo-sphenoidal lobes and the optic thalami of the two sides. 



3. Fibres connecting Different Cerebral Convolutions on the Same Side 

 (Association Fibres). (A) Arcuate fibres, passing from one convolution 

 to another, connect adjacent convolutions. (B) Longitudinal fibres con- 

 nect distant convolutions. The fibres of the fornix connect the optic 

 thalamus with the hippocampus major and the uncinate gyrus. Fibres 

 in the corpus callosum connect the anterior and posterior extremities of 

 the gyrus fornicatus. These are the longitudinal fibres of the corpus 

 callosum. Other longitudinal fibres, connecting parts more or less dis- 



