468 ANATOMICAL TECHNOLOOY. 



The left medicornu is cut at about tlie middle, and at nearly a riglit angle witli its 

 course ; hence its lumen presents its characteristic crescentio section, the ental boundary 

 being the convex surface of the hypocampa Qimp.). 



The cephalic margin of the medicornu is here seen to reach the surface of the hemi- 

 sphere close to the Tractus opticus, and this narrow line of interruption of the true ner- 

 vous wall of the cornu constitutes the rima. The scale upon which this figure was drawn 

 did not permit the relations of the pia, the nelum and the proplexus to be shown, and the 

 undulations of the ectal surface, corresponding with the JfF. hypocampx and fimhricB, and 

 the fagciola and fimbria are hidden by the projecting postgeniculatum. 



Most of the cephalic portion of the brain has been removed, but the Portio depressa 

 {PL d.) of the praeperforatus is seen, with part of the Pt. prominens (Pt. p.). The 

 removal of most of the chiasma (cJi.) exposes the form and extent of the Recessus opticus 

 {B. op.). 



The pons has been transected obliquely, and its caudal portion removed, together with 

 the rest of the epen. and the metencephalon. 



The left crus {Gr. cb.) is seen in its whole length, excepting a small part concealed by 

 the slightly projecting cephalic border of the pons. The well marked cimbia (cmb.) may 

 perhaps be regarded as the boundary betweea the diencephalic portion of the crus (Pt. 

 dien.) and the mesencephalic portion (Pt. msen.), which more directly supports the optici 

 and postoptici ; in man, this part seems to be more nearly concealed by the pons. 



The^right N. oculomotorius (iV. ocm.) is seen to emerge from the crus just caudad of 

 the mesal end of the cimbia and just laterad of the Sulcus intercruralis lateralis (SI. 

 ic. I.). A marked longitudinal ridge of the crural fibers separates from the postgenicu- 

 latum ( pgn) a depressed area, the quadrans (?.). 



The albicantia {abn.) are more closely united than in man, but large, white and per- 

 fectly distinguishable. The shallow furrow between them, together with the u-shaped 

 furrow which forms their cephalic boundary, is the Sulcus triradiatus (81. trd.). 



The hypophysis has been removed so as to expose the Tuber cinereum (T. cin.) and 

 the thin raised margin of the Fm. infundibuli (Fm. inf.). 



Just caudad of the albicantia, and partly overhung by them, is a small triangular 

 depressed space vrith distinct perforations ; this seems to be the true postperforatus 

 (PPf-l 



The entire Area intercruralis may be more completely exposed by removing the cere- 

 bellum and dorsiducting the " medulla," as in Prep. 435. 



§ 1170. Fig. 12. — The dorsal aspect of the metencephalon. From Prep. 397 

 (adult s ), 464 and 491 ; x 1. 



" The metatela, like the diatela, seems to consist of more substantial tissue than sim- 

 ply pia and endyma, but I am not aware that its microscopic structure has been ascer- 

 tained. I am in doubt respecting the precise limits and attachments of the metatela 

 and metaplexuses." No " foramen of Magendie " was seen. 



§ 1171. Fig. 13.— Part of an oblique transection of the prosencephalon and dien- 

 cephalon to show the form and position of the Crista. Prom Prep. 441 ; x 2. 



The brain was transected obliquely at an angle of about 45 degrees with the general 

 longitudinal axis. The plane of section passed from a point nearly dorsad of the genu, 

 through the aula, the medicornu and the albicantia. The figure includes only a part of 

 the caudal aspect of the slice. 



The dorsal borders of the hemispheres are divaricated slightly, and the calfosum (cl.) 

 is seen crossing the interval ; the slight notch on each side just dorsad of the callosum is 

 the F. callosalis (F. cl.). 



