636 



PHYSIOLOGY. 



of the pons. At a slightly higher level is found another, known as 

 the central nucleus. To these two nuclei are joined, in part, the root- 

 bundles of the antero-lateral column of the cord. 



In addition, as a continuation of the anterior horns of the cord, 

 there exists a nucleus which gives origin to the trigeminus. Inward 

 and somewhat to the front is found a gray mass composed of large 

 multipolar cells. These represent the caput of the anterior horn. 

 It forms the nucleus of origin of the motor root of the trigeminus. 



Upon each side of the raphe and very close to the surface of 

 the floor of the fourth ventricle are found other gray nuclei, as of 

 the facial and abducent; also a yellow mass of an S-shape which 



12 3 456 7 



11 10 9 8 



Fig. 247. Diagrammatic Transverse Section Through the Cms 

 Cerebri and Anterior Corpora Quadrigemina. (WALLER, after OBER- 



STEINER.) 



The letters a m p on the pes or crusta signify portions occupied by fibers from 

 the anterior, middle or rolandic, and posterior regions of the cortex. 



1, Pulvinar. 2, Corpus genie, lat. 3, Corpus genie, med. 4, Corpora quad, 

 ant. 5, Sylvian aqueduct. 6, Tegmentum. 7, Crusta. 8, Substantia nigra. 9, 

 Red nucleus. 10, Third nerve. 11, Optic tract (divided). 



forms the superior olive of the pons. This latter is connected with 

 the auditory apparatus. The gray substance of the medulla is pro- 

 longed into the pons to form the origin of the cranial nerves. 



Cerebral Peduncles. 



The peduncles of the brain are two white cords which extend 

 from the superior face of the pons in a divergent manner up into the 

 optic thalami. They are somewhat flattened from top to base. Their 

 volume is in direct relation to that of the brain. The peduncles 

 are much larger than the columns of the cord reunited; they con- 



