Anatomy of the Brain. 557 



connected with the overlying pia mater. This has been termed the sub- 

 stantia pcrforata. It, in part, forms the base of the corpus striatum. 

 Just in front of the cerebellum, and on top of the cerebral peduncles, 

 are the corpora quadrigemina. These consist of two bulbs of nervous 

 matter on each side. The hinder one is the smaller. It has a core of 

 gray vesicular matter covered by a coat of white substance. It is called 

 the testis. Joining it in front is the other, called the natis. An oblique 

 band of nerve fibre passes from the testis outwardly past the natis, and 

 connects with the corpus geniculatum interim m of the optic thalamus. 

 The nates are larger than the testes, and composed of gray matter al- 

 most entirely, the white coat being thin. In the lower part of each one 

 of the nates is a vesicular nucleus called the red nucleus or nucleus teg- 

 mentum. These nuclei are the forward terminations of the anterior pe- 

 duncles of the cerebellum, which pass from the cerebellum under the 

 testes, and enter these red nuclei. The part of the lateral external face 



FlG. 274. 



FIG. 274. Frontal cross section of Corpora Quadrigemina of monkey, at the origin of 

 third nerves. ( Ferrier, after Bevan Lewis.) 



C Crusta or foot of cms cerebri. SN. Substautia nigra, or locus niger 



FL. Posterior longitudinal fasciculus. ( black place ). 



MO Nucleus of motor oculi, or 3rd nerve. V. Aqueduct of sylvius surrounded by 

 N Nates central gray substance. 



RN. Red Nucleus or Nucleus Tegmenti. III. Roots of the 3rd nerve ( motor oculi). 



of the cerebral peduncle which lies beneath the testis, forms a triangular 

 tract called the band of Rcil. On the median line, under the corpora 

 quadrigemina and above and between the peduncles, is a longitudinal 

 opening leading from the fourth ventricle in the rear, to the third ven- 

 tricle in front. It is called the aqueduct of sylvius. 



The corpora quadrigemina are the ganglions of sight. The nervous 

 tissue composing them is intimately connected and confounded with the 

 substance of the inner sides of the crura or peduncles ; such connection 

 giving chiefly sensory stimuli. But besides this, the testes have connec- 

 tion with the motor tract by means of fibres to the olivary bodies, which 



