PARTS DERIVED FROM THE FORE-BRAIN 317 



ing the aqueduct at its continuation into the third ventricle. 

 It contains decussating and connecting fibers (1) for the median 

 longitudinal bundle ; (2) the two thalami ; (3) the habenula nidi ; 

 and (4) the superior quadrigeminal bodies. 



(NOTE. The habenulse, pineal body, and posterior com- 

 missure are generally included under the head of epithalamus.) 



The hypothalamic tegmental substance is continuous with 

 the mid-brain tegmentum. It is found between the ventral 

 face of the thalamus, the red nucleus, and a continuation of 

 the substantia nigra known as the corpus hypothalamicus, or 

 body of Luys. The fibers contained within the hypothalamic 

 tegmentum communicate with the medial lemniscus, of the 

 superior peduncle of the cerebellum, and from the red nucleus 

 to end in relation with the thalamic cells. The corpus hypo- 

 thalamicus lies frontad to the lateral part of the substantia 

 nigra, and, like it, is situated between pes and tegmentum. 

 Its fibers decussate in the floor of the third ventricle with 

 those of the opposite side, dorsocaudad of the corpora albi- 

 cantia. 



The corpora albicantia are two bodies placed side by side 

 in the intercrural space, cephalad of the posterior perforated 

 substance, at a point where the floor of the third ventricle 

 becomes decreased in thickness to form the tuber cinereum. 

 They are white in color, due to a superficial layer of fibers 

 derived from the fornix. The fibers of the fornix terminate 

 in the corpora albicantia. 



The posterior perforated substance marks the situation of 

 the interpeduncular ganglion. From it arise the fiber tracts 

 called the tsenia pontis. It occupies the interval between the 

 copora albicantia, the pons, and the crura cerebri. 



(NOTE. The corpora albicantia and the posterior per- 

 forated substance are generally included under the head of 

 the Pars Mammillaris Hypo thalami.) 



The parts found under a description of the telencephalon 

 include the pars opticus hypothalami, consisting of the tuber 

 cinereum, the pituitary body, or hypophysis, the infundibulum, 

 the lamina terminalis, the optic chiasm, and the optic tract. 



The tuber cinereum is an elevation of gray matter between 

 the optic tracts and the corpora albicantia, and forms part 

 of the floor of the third ventricle. Its apical portion is atten- 

 uated, and forms the stalk of the pituitary body; the latter is 



