CRANIAL CAVITY. 



the dorsum of the crusta replaces the substantia nigra ante- 

 riorly. [546] 



Pineal Body. This is a conical, reddish body lying in a de- 

 pression between the superior quadrigeminal bodies. At its 

 base is a hollow stalk divided, by a recess of the third ven- 

 tricle, into a ventral part folded round the posterior com- 

 missure, and a dorsal part curving outward on each side to 

 join the tsenia thalami and stria medullaris. Trigonum haben- 

 ulae: This is a small triangular depression between the pin- 

 eal stalk, superior quadrigeminal body, and optic thalamus. 

 Stria medullaris: This is a white band on the thalamus, 

 under the taenia thalami; posteriorly it partly ends in the 

 ganglion habenulse, and partly crosses in the dorsum of the 

 pineal stalk (commissura habenularum) to the opposite gan- 

 glion habenulae ; anteriorly it divides, near the anterior pil- 

 lar of the fornix, into a dorsal part running upward to the for- 

 nix, and a ventral part running downward to nerve cells. 

 Gommissura posterior: This is a slender white band which 

 crosses the midline, between the pineal stalk and orifice of the 

 Sylvian aqueduct. [547] 



Interpeduncular Space. This is a deep lozenge-shaped inter- 

 val between the crura cerebri, optic tracts, and optic chiasm. 

 The locus perforates posticus, a layer of central gray matter with 

 many foramina, forms the floor of the posterior angle ; delicate 

 white bands (taenia pontis) pass from it, around the crura 

 cerebri, to the pons. The corpora mammillaria are two small 

 and round white bodies lying side by side just in front of the 

 preceding; they consist of gray matter, covered by white 

 matter from the fornix. The tuber cinereum is an elevated 

 area of central gray matter which stretches from the corpora 

 mammillaria to the optic chiasm. From its fore part the 

 stalk (infundibulum) of the pituitary body projects down- 

 ward, being hollowed above by a recess of the third ventricle. 

 The pituitary body is small, oval, and formed by two lobes; 

 the posterior, which receives the infundibulum, is chiefly con- 



[35] 



