ANATOMY AND PHYSIOLOGY OF NERVOUS SYSTEM. 



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tain fibers coming from the gray matter of the medulla, pons, cor- 

 pora quadrigemina, locus niger, and masses of gray matter lying in 

 a line along the aqueduct of Sylvius. In length the peduncles meas- 

 ure about three-fourths of an inch. 



Immediately after their emergence from the pons they separate, 

 each one making its way toward its corresponding hemisphere of the 

 cerebrum. Between them there remains a triangular space, the 

 interpeduncular space, filled in its back part by a cribriform white 

 layer containing a great number of vascular openings. The latter 

 is known as the posterior perforated space. This space, bounded in 



Fig. 248. Section of the Crus Cerebri. (MORAT.) 

 The crusta is separated from the tegmentum by the locus niger. 



1, Aqueduct. 2, Corpora quad. 3, Vent gray matter. 4, Red nucleus. 5, 

 Locus niger. 6, Crusta. 7, Furrow for the oculo-motor nerve. 8, Sub. perforat. 

 posterior. 



front by the optic chiasm, is occupied by the mammillary eminences 

 and tuber cinereum. 



Texture of the Peduncles. A transverse section of the cerebral 

 peduncles gives an idea of the architecture of the large nerve-trunks. 

 In a cut of this kind it is seen that the peduncles are separated into 

 two white, superposed layers by a black line : the locus niger. 



The inferior level, or crusta, of the peduncle is formed in great 

 part by a large, flat, white bundle which is a prolongation of the 

 motor fibers extending to the spinal cord. The crusta extends from 

 the internal capsule through the pons to the ventral portion of the 

 ledulla oblongata. From the internal capsule its fibers become lost 

 in the cortical layer of the hemisphere of its own side. 



The crusta is composed of two bundles, the internal, or cortico- 



