THE NERVOUS SYSTEM. IQl 



transverse fibers which on either side forms the middle 

 peduncle of the cerebellum, commonly called the crus 

 cerebelli ad pontem medullse. The fibers originate either 

 in cells of the medulla or those of the cerebellum. 



The crura cerebri, or peduncles of the cerebrum, the 

 ventral portions of which are continued as the anterior 

 pyramids (Fig. 90), are seen just cephalad of the pons. 

 Their fibers unite the cerebrum to the rest of the brain 

 and the spinal cord. In the space between the crura 

 and the optic chiasm is a prominent projection, the 

 terminal nodular portion of which is the pituitary body 

 or hypophysis. It occupies the pituitary fossa of the 

 skull and is usually torn off in removing the brain. 

 Caudad of the hypophysis are two small rounded white 

 bodies, the corpora albicantia. The tuber cinereum, a 

 slightly elevated mass of gray matter behind the optic 

 chiasm, bears on its surface the funnel-shaped stalk, the 

 infundibulum , to which the hypophysis is attached. If 

 the two latter parts are removed, there is seen a small 

 elongated aperture through the tuber cinereum into the 

 third ventricle (Figs. 90 and 92). 



The optic commissure, or optic chiasm, is the commissure 

 formed by the crossing of the optic nerves just cephalad 

 of the tuber cinereum. The prolongation of the optic 

 nerves dorsad from the optic commissure forms the 

 optic tracts, partly covered by the temporal lobes. On 

 either side of the median fissure just cephalad of the 

 optic chiasm is a somewhat triangular area known as 

 the anterior perforated space because of the numerous 

 vessels that enter the brain in this region. Laterally this 

 space is bounded by the lateral olfactory tract or lateral 

 root of the olfactory nerve, which presents the appearance 

 of a band of white fibers extending from the olfactory 

 lobe into the temporal lobe. The mesal or inner root of 



