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NERVOUS SYSTEM 



to the internal surface' of the cerebral convolutions, they form the 

 corona radiata. 



In the human subject, lesions affecting the anterior two-thirds of 

 the posterior division of the internal capsule produce paralysis of 

 motion only and are followed by descending degenerations. The 

 fibres in this part are connected with the corpora striata. Lesions 

 affecting both the anterior two-thirds and the posterior third of the 

 posterior division of the internal capsule produce paralysis of motion 

 and sensation. The fibres in the posterior third are connected with 



Fig. 142. Vertical section of the brain, reduced about one-quarter (Dalton). 



the optic thalami. Ascending degenerations have not been observed 

 in the fibres of the cerebrum. 



Tubercula Quadrigemina. These little bodies, sometimes called 

 the optic lobes, are rounded eminences, two on either side, situated just 

 below the third ventricle. The anterior, called the nates, are the larger. 

 These are oblong and of a grayish color externally. The posterior, 

 called the testes, are situated just behind the anterior. They are 

 rounded and are rather lighter in color than the anterior. Both contain 

 gray matter in their interior. They are the main points of apparent 

 origin of the optic nerves and are connected by commissural fibres with 

 the optic thalami. In birds the tubercles are two in number, instead 

 of four, and are called tubercula bigemina. 



