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 (I*. transversa) begins a little 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.! 
- 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. 
: Transverse Calloso-mar- 
Gyrus fornicatus Jissure ginal fissure 
\ 
Callosal 
sulcus~ 
° rs 
Anterior com- ‘ \ 
missure Lamina  Chiatma 
h 
L 
\ 
\ F ! 
{Posterior | \ \ 
: 
oo, , - - ' 
terminals opticum \ : 
AMT SOE Anterior Fourth 
Cerebral. medul- ventricle 
aqueduct - lary 
velum 
Hypophysis 
cerebri 
Fic. 639.—Mep1an Section oF Brain oF Horse. 
The membranes and vessels are removed. C, Central white matter (corpus medullare) of cerebellum; P.c., cere« 
bral peduncle; C.g., corpora quadrigemina; P, pineal body; Th., thalamus; V-III., third ventricle; 7, optic recess; 
r’, infundibular recess; C.m., mammillary body; s, subcallosal gyrus; A.p., area parolfactoria; G, genu of corpus 
callosum; S, splenium of same; F.i., interventricular foramen; B.o., olfactory bulb; C.p., choroid plexus of lateral 
ventricle. 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 optie 
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, 7. 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 
1 By some authors 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. 
2 Also termed the cornu Ammonis. 
