ANATOMICAL DESCRIPTION 287 



with which are connected the olfactory nerves (Fig. 134). 

 They are direct outgrowths of the brain substance. Lying 

 partly in the lateral ventricles ( 426) and partly embedded 

 in white substance of the hemispheres, are the pear-shaped 

 corpora striata (Fig. 130), composed of white and gray 

 matter. They are ganglia on the path of motor nerves. 



422. The Optic Thalami are masses of gray matter in the 

 base of the cerebrum (Fig. 130), and are closely con- 

 nected with the corpora striata, which belong to the cere- 

 brum. These two pairs of gray bodies are often called the 

 basal ganglia. From them nerve fibers radiate into the 

 convolutions of the cerebral hemispheres. The optic thai- 

 ami are ganglia on the path of sensory nerves ; the corpora 

 striata belong to the motor tract. 



423. The Corpora Quadrigemina, or Optic Lobes, and the 

 Crura Cerebri. The corpora quadrigendna, or optic lobes, lie 

 behind and between the optic thalami (Figs. 129 and 130). 

 They are masses of gray matter, or rather a single body 

 divided by shallow fissures into four hemispherical parts. 

 The optic tracts arise superficially from their surfaces. 

 The optic lobes rest upon the hinder face of the crura 

 cerebri. These latter are bundles of nerve fibers forming 

 peduncles, or stalks, which connect the cerebrum with 

 other parts of the brain. 



424. The Cerebellum and Pons Varolii (Figs. 129 and 

 134). The cerebellum is composed of gray and white 

 matter, and lies in two hemispheres across the back of the 

 cerebro-spinal axis. The hemispheres are connected by 

 bands of white matter, called peduncles, with each other 

 and with other parts of the brain. The white matter of 

 the cerebellum is arranged on each side in a central trunk, 

 which divides into many branches, around which the gra}^ 

 matter is placed, the whole forming what is called, from 



