494 



ANATOMICAL TEOSNOLOOT. 



the combined hemispheres are approximately equal, and the height 

 is about three fourths as much. 



As compared with most dogs, also, the region cephalad of the 

 cruciate fissure is very short. 



•s S i 



THE CEREBRAL FISSURES. 



§ 1336. References. — The principal works and papers ill which the cerebral fissures are 

 treated of are named in connection with the synonymy of the IP. eruciata (§ 1361). 



§ 1337. As was remarked in § 1131 (17, 18), the brain of the cat difEers from that of 

 the Amphibia in that the hemispheres and cerebellum are not only larger in proportion, 

 but convoluted — the surface presenting depressions (fissurce) and intervening folds {gyri). 



The cerebellar fissures are numerous and apparently irregular ; and we are not aware 

 that their arrangement has been studied in detail. 



The cerebral fissures are comparatively few (about 30) and simple, so that it is not 

 difficult to delineate or describe them as they appear upon a given brain. 



§ 1338. The fissures should be studied before the gyri. — Notwithstanding the prob- 

 ability that the fissures are only the results of the outgrowth constituting the gyri, and 

 the fact that experiments are made upon the exposed surfaces of the latter, the study of 

 cerebral topography should begin with the fissures, and they should be identified and 

 named before the gyri are described and designated. As remarked by the senior author 

 (11, 219), the " sides of a fissure are usually near together and parallel, so that the fissure 

 may be described as a single line of certain direction ; but the opposite borders of any one 

 gyrus are rarely parallel throughout their whole extent. Indeed, It would be as hard to 

 designate gyri without first identifying fissures as to describe the countries of Europe 

 without mentioning its rivers." 



Fig. 124, 125. — Diageams of the Lateral and Mesal Aspects of the Hemi- 

 spheres, SHOWING THE FISSURES ; X 1.5. 



Pig. 124. — Diagram of the lateral aspect of the left hemisphere, showing the fissures; 

 xl.5. 



Fig. 125. — Diagram of the mesal aspect of the right hemisphere, showing the fissures. 

 The diencephalon and the segments caudad of it have been removed as in PI. IV, Fig. 17, 

 so as to expose the F. Jiypocampee and the adjacent parts ; x 1.5. 



On both the figures too little distinction is indicated between the constant and the 

 inconstant fissures. Upon the Table (p. 496) the former are printed in heavier faced type, 

 and they are enumerated in § 1366. 



