778 NERVOUS SYSTEM OF THE HORSE 
to the tegmentum of the cerebral peduncle, the hypothalamic region, and the thalamus. After 
the peduncles disappear under the corpora quadrigemina, they converge and many of their fibers 
intercross, forming the decussation of the anterior peduncles. A considerable number of fibers 
end in the nucleus ruber. Thence impulses are transmitted in two directions: first, by thalamo- 
cortical fibers to the cerebral cortex; second, by the rubro-spinal tract through the brain stem 
and lateral columns of the cord to the ventral horn cells. The ventro-lateral cerebellospinal 
fasciculus (Gowers’ tract) is an ill-defined tract which connects the spinal cord with the cere- 
bellum. Its fibers appear to be axones of cells of the dorsal columns of the cord; they pass 
in the lateral column of the cord, become scattered in passing through the reticular formation 
of the medulla and pons, and enter the cerebellum by way of the anterior medullary velum. 
THE FOURTH VENTRICLE 
The fourth ventricle (Ventriculus quartus) is the cavity of the rhombencepha- 
lon; it communicates with the central canal of the spinal cord behind and through 
Corpus callosum (section) Lateral ventricle 
A . a, 
Septum pellucidum 
Nucleus caudatus 
Thalamus (anterior 
tubercle) 
Stria terminalis 
Corpus geniculatum 
ae laterale 
Plexus chorioideus 
Corpus quadrigeminum 
Corpus geniculatum mediale 
antertus 
Pedunculus cerebri 
Corpus quadrigeminum 
postertus 
_— Velum medullare anterius 
y 
Brachium conjunctivum 
Brachium pontis 
VOL. 
“IL 
Tube roulu me acusticum 
Pld So : 
cenia ventriculi quart : 
i so Corpus restiforme 
Calamus scriptorius 
Obex 
——— Tuberculum cinereum 
Fissura mediana 
Fic, 635.—DissecTion oF Bran STEM AND Basat GANGLIA OF Horse; DorsaL VIEW. 
1, Columns of fornix (section); 2, remnant of hippocampus; 3, tenia thalami; 4, pineal body; 5, eminentia medialis; 
E y Zs res s : ; . 
6, suleus medianus; 7, suleus limitans; V ITI., third ventricle; Vit ., fourth ventricle. Stumps of cranial nerves are 
indicated by Roman numerals. 
the cerebral aqueduct with the third ventricle in front. It is somewhat rhomboid 
in outline, elongated from before backward, and narrowest behind. It is lined 
completely by an epithelium (Ependyma) and contains a small amount of fluid. 
Its floor, the fossa rhomboidea, is formed by the medulla oblongata and pons 
