THE CEBEBRUM. 



787 



that of Rolando ; it is directed forwards, outwards, and downwards — that is to say, 

 it turns round the anterior extremity of the hemisphere to terminate near the 

 fissure of Sylvius. Within this fissure is a triangular convolution, with its 

 summit directed backwards ; it is generally divided into two folds at its inferior 

 part — this is the first frontal convolution (Figs. 428, 9 ; 438, 15, 15). 



Another convolution is included between this fissure and that which margins 

 the ascending frontal convolution ; it is doubled into two wide flexuous folds 

 which pass into the latter in front, and represents the second frontal convolution 

 (Figs. 423, 10, 10; 483, 14, 14). 



BRAIN OF THE HORSE (LATERAL FACE). 



B, Medulla oblongata; Pr. pons Varolii; Pc, cerebral peduncle {cms cerebri). 1, Middle lobe ot the 

 cerebellum; 2, lateral lobe of ditto; 3, medullary root of the spinal accessory nerve; 4, internal 

 roots of ditto and roots of the pneuraogastric ; 5, transverse fasciculus of the medulla oblongata, 

 at the extremity of which the facial nerve appears to arise ; 7, fissure of Sylvius ; 8, 8, 8, 

 fissure of Rolando; 9, posterior branch of ditto; 10. lobule of the curved plait; 11, 11, 11, 

 limiting frontal convolution; 12, 12, parieto-temporal convolution (analogous tn the ascending 

 parietal convolution); 13, second parieto-temporal convolution; 14. 14. the two juincipal folds 

 of the second frontal convolution; 15, 15, folds of the first frontal convolution; 17, ]iarieto- 

 occipital lobe; 18, inferior temporal convolution (2nd and 3rd of Man); 19, superior tempnral 

 convolution (1st of man); 20, intra-ventricular nucleus of the corpus striatum ; 21, external root 

 of the olfactory lobule ; 22, olfactory nerves. 



The third convolution seen in Man is not defined in the Horse by an impor 

 tant fissure, and if it exists in this animal it is probably represented by the origin 

 of the inferior fold of the second convolution, which is sometimes separated from 

 the rest by a shallow sulcus. 



The internal face of the frontal lobe shows the internal part of the first 

 frontal convolution, and a portion of the calloso-marginal Jissure and crested 

 convolution. 



c. Temporal or sphenoidal lobe. — Also named the mastoid lobule by Veterinary 

 Anatomists, the temporal lobe in Solipeds is a large pyrif orm eminence occupying 



