190 



DISSECTION OF THE BRAIN. 



without any large cleft ; but inferiorly it is divided into two by a trans- 

 verse fissure that of Sylvius. 



UNDER SURFACE OR BASE OF THE CERKBRUM (fig. 59). At its under 

 part the cerebrum is very irregular, in consequence of its fitting into in- 

 equalities in the base of the skull ; and on this aspect the separation into 

 hemispheres is not so complete as on the upper, for the median fissure 

 exists only at the front and back. The following objects are to be recog- 

 nized at the base of the brain along the middle line. 



Fig. 59. 



Q> 



-a 



UNDER SURFACE OF THE BRAIN. 

 6. Cerebellum. 



r. Temporo-sphenoidal lobe of the cerebrum. 

 p. Frontal lobe of the cerebrum : the great fis- 

 sure between the two lobes, is the Syl vian. 

 a. Medulla oblongata. 



d. Pons Varolii. 

 /. Crus cerebri. 



g. Locus perforatns posticus. 



e. Corpus albicans. 

 h. Tuber cinereum. 



i. Commissure of the optic nerves. 



I. Locus perforatus anticus. 



7n. Lamina cinerea. 



n. Lower end (rostrum) of the corpus callosum 

 in the great median fissure; the point iu 

 front where it bends is named genu. On 

 eac-h side of the lamina ciuerea a narrow 

 white band is continued from the end of 

 the corpus callosum : this is the fillet of 

 the corpus callosum. 



Immediately in front of the pons (d) are two large white masses, the 

 peduncles of the cerebrum (crura cerebri, /), one belonging to each hem- 

 isphere ; and between is a space perforated by vessels, which is named 

 locus perforatus posticus (g}. Outside the peduncle is the optic tract (i) ; 

 and between it and the inner part of the hemisphere is a fissure leading 

 into the lateral ventricle. 



In front of the peduncles are placed two white bodies like peas, the 



