DISSECTION OF THE HEAD AND NECK 331 



(ab) Intermediate part (pars intermedia fossae rhomb oideae) . 



(aba) Lateral recess (recessus lateralis fossae rhom- 

 boideae). 



(ac) Superior part (pars superior fossae rhomb oideae) . 



(ad) Limiting groove (sulcus limitans [fossae rhomb oideae]) . 



(ada) Inferior pit (fovea inferior). 



(adb) Superior pit (fovea superior). 



(b) Trigone of hypoglossal nerve (trigonum N. hypoglossi). 



(c) Medullary striae (striae medullares) (0. T. striae acusticae). 



(d) Medial eminence (eminentia medialis) (0. T. eminentia teres). 



(e) Facial hillock (colliculus facialis). 



(f) Ash-like wing (ala cinerea) (0. T. trigonum vagi). 



(g) Acoustic area (area acustica) (0. T. trigonum acustici). 

 (h) Locus caeruleus (locus caeruleus) ("blue place"). 



(i) Roof of fourth ventricle (tegmen ventriculi quarti). 



(ia) Posterior medullary velum (velum medullare posterius). 

 (ib) Junction of epithelial part of roof with compact nerve sub- 

 stance (taenia ventriculi quarti). 

 (iba) Obex (pbex) ("bar"). 

 (ic) Epithelial chorioid layer (lamina chorioidea epithelialis) . 



(ica) Median aperture (apertura mediana ventriculi 



quarti [foramen Magendii]). 

 (icb) Lateral aperture (apertura lateralis ventriculi 



quarti). 

 (id) Fastigium (fastigium) (" summit of roof "). 



External Morphology of Forebrain (Prosencephalon). 



Cut cautiously through the remaining cerebral peduncle and 

 place the rhombencephalon and the mesencephalon in preserving 

 fluid for further study later. In the prosencephalon distinguish 

 the following parts : 



Forebrain (prosencephalon). 

 Interbrain ( diencephalon) . 



Thalamic brain (thalamencephalon). 



Mammillary part of hypothalanms (pars mammillaris hypothalami). 

 End-brain (telencephalon) . 



Hemisphere ( hemisphaerium ) . 



Optic part of hypothalamus (pars optica hypothalami). 



Make three drawings of the half of the prosencephalon before 

 you 



(a) Of medial surface (fades medialis cerebri). (Fig. 151.) 



(b) Of convex surface (fades convexa cerebri). (Fig. 149.) 



(c) Of base (basis cerebri). (Fig. 150.) 



Take up systematically the study of the external morphology 

 as follows : 



