PHYSIOLOGY: PRACTICUM VIII: PLATE XVIII. 



THE BRAIN OF THE SHEEP, THE CEREBRUM SLICED TO NEAR THE LEVEL 



OF THE CALLOSUM ; /. 1.5. 



--olfactory bulb inclosing rhinocoele 



genu (of callosum) 

 cortex (cinerea) 

 medulla (alba) 



Sylvian fissure 



callosum 



2 



--3 



splenium (of callosum) 



7 



-vermis imesal lobe) 

 lateral lobe 



postoblongata 



myel (spinal cord) 



The following points are illustrated : 



A. The general proportions of the two great masses, CEREBRUM and CEREBEL- 

 LUM. 



B. The constitution of the cerebellum by a mesal lobe (VERMIS) and a pair of LAT- 

 ERAL LOBES. 



C. The junction of the two halves of the cerebrum by a thick sheet of fibers, the 

 CALLOSUM ; its rounded cephalic and caudal margins are the GENU and SPLENIUM, 

 respectively ; PI. XXIII. 



D. The relative positions of the two kinds of substances in the larger part of the 

 .cerebrum ; the ALBA (white substance) is central ; the CINEREA (gray substance) is per- 

 ipheral, constituting the CORTEX. 



E. The relation of the cortex to the FISSURES. 



F. The passage of the ARACHNOID membrane across the mouths of the fissures, as 

 at i and 4, while the PIA dips to the bottom as a fold. 



G. The existence of a cavity (RHINOCCELE or olfactory ventricle) in the OLFAC- 

 TORY BULB ; see PI. XXIV and p. 69, Fig. 3. 



Defects. The cerebellar divisions (FOLIUMS) are not shown in detail. In the dark 

 interval (6) between the cerebellum and cerebrum should appear the cut ends of vessels 

 one of which is shown in PL XXIV. There is no indication of the thin layer of cinerea on 

 the dorsum of the callosum ; PI. XXV. 



