786 



NERVOUS SYSTEM OF THE HORSE 



for the corpora quadrigemina. It separates the marginal gyri above from the gyrus 

 fornicatus, which extends down to the corpus callosum. 



2. The transverse fissure (F. transversa) begins a httle behind the middle of 

 the calloso-marginal fissure, passes obliquely dorsally and forward to the dorso- 

 medial border — into which it cuts deeply — and usually joins the suprasylvian 

 fissure. 1 



3. The sublimbic fissure (F. sublimbica) curves over the gyrus fornicatus a 

 short distance above the corpus callosum. Its middle part is commonly indistinct, 

 and it is often divided into anterior and posterior parts. 



Gyrus fornicatus 



Transverse 

 fissure 



Calloso-rnnr- 

 ginal fissure 



Marginal fissure 



Callosal 

 sulcus^ 



Entoviarginal fissure 



Anterior com- 

 missure Lamina 

 terminalis 



Clilasma 

 optician 



I 



\ 



1 I'nslerior 



; couinassur. , ^,,,,rio^ 

 Hvvophysis '^^'^relral medul- 

 ' cerebri aqueduct lary 



Fourth 

 rentricle 



velum 

 -Median Section of Bhain of Horse. 

 \^ed. C Central white matter (corpus medullare) of cerebellum; P.c, cere- 



Fig. 630.- 

 The membranes and vessels are remov 

 bral peduncle; C.q., corpora quadrigemina; P. pineal body: Th., thalamus; V.III., third ventricle ; r, optic recess; 

 r', infundibular recess; Cm., mammillary body; s, subcallosal gJTUs; A.p., area parolfactoria; G, genu of corpus 

 callosum; S, splenium of same; F.i., interventricular foramen; B,o., olfactory bulb. The cerebral lobe of the 

 hypophysis cerebri or pituitary body is distinguished by its lighter color. 



4. The callosal sulcus (Sulcus corporis callosi) separates the corpus callosum 

 from the gyrus fornicatus. 



The hippocampus^ is a gyrus which curves from the deep face of the piriform 

 lobe around the thalamus and forms the posterior part of the floor of the lateral 

 ventricle. It can be displayed by cutting away the brain stem up to the optic 

 tract and the interventricular foramen. Viewed from below, the hippocampal 

 gyrus is seen to form a semicircular curve from the apex of the piriform lobe to 

 the angle of divergence of the crura of the fornix, i. e., to a point under the central 

 part of the corpus callosum. It is separated deeply by the hippocampal fissure 

 from the gyrus dentatus (Fig. 640). Along the concave margin of the latter is a 



' By some autliors this is regarded as the homologue of the cruciate fissure of the dog, but it 

 seems likely that the latter is represented by a short and inconstant sulcus situated further forward. 

 ^ Also termed the cornu Ammonis. 



