PHYSIOLOGY : PRACTCUM IX : PLATE XXV. 

 A. TRANSECTION OF SHEEP'S BRAIN ; X 1.5. 



_ _ arachnoid 



iS^c- intercerebral fissure 



--splenial f. 



'_ V <-:illi>s:il I. 



,_ paracoele 

 para plexus 



'- FORNIX 



;*/-- HABKNA 

 'fJf-- MEDICOMMISSTRK, 

 diacoele 



rhinal f. 



.optic tract 

 olfactory tract 



The plane of section approximates E in PI. XXIII. The HYPOPHYSIS has been re- 

 moved and the DIACCELE is open ventrad at the LURA (PI. XX). The OPTIC TRACT is 

 cut obliquely ; its fibrous structure is roughly indicated by lines. The masses connected 

 by the MEDICOMMISSURE are the THALAMI. The CALLOSUM is indicated by lines. 

 The INTERCEREBRAL FISSURE is bridged by the ARACHNOID ; in man the falx de- 

 scends into the fissure for a greater or less distance carrying the arachnoid before it. The 

 fissure here named rhinal is named olfactory in PI. XIX. 



B. ENLARGEMENT OF THE CENTRAL REGION OF A. 



intercerebral f. 



C A L L S UM 



callosal fissure 

 -} callosal ciiierea 



ENDYMA 

 paracoele 

 PSEUDOCCELE 

 HEMISEPTUM 



for u icom niissu re 



VELUM 



velar vein 



RIPA 



DIATELA 



DIAPLEXUS 



diaccele 



medicommissure 



This was designed to exhibit more clearly the relations of the CAVITIES to the MEM- 

 BRANES and PLEXUSES, but some points are obscured by the shading. 



The mesal DIACCELE and the laleral PARACCELES are lined by smooth ENDYMA, 

 represented by a heavy line. In the diacoele the enclyma may be traced dorsad upon the 

 mesal surface of the THALAMUS and over the dorso-mesal ridge representing the HAB- 

 ENA, as far as the point called RIPA, (see PI. XXII, left side.) Here it is reflected mesad 

 upon the ventral surface of the VELUM 



The velum consists of the PI A covering the ventral surface of the FORNIX and the 

 dorsal surface of the thalami. together \*ith CONNECTIVE TISSUE and VESSELS (of 

 which only one is shown). Near the meson there hangs into the diacoele at each side a 

 plexus (DIAPLEXUS) covered by the endytna. 



At the interval (RIMA) between the margin of the fornix and the caudatum (i) the 

 velum extends into the paracoele as the PARAPLEXUS, covered, however, by the endyma 

 which is reflected off at 3 and the point opposite. 



A thin layer of the cortex extends across the callosum. 



