STUDY OF THE FISSURES. 495 



1339. Study of the Fissures. The student should make outline drawings of one 

 or more hemispheres, especially of the lateral aspect. If possible, both hemispheres of 

 the same brain should be drawn and compared with respect to the amount and character 

 of lateral variation and compensation (Wilder, 11, 232). The sex should always be 

 noted, and the age, known or estimated, stated upon the drawing. 



The drawings of fissures should be in outline only, and most attention should be given 

 to the union or independence of fissures which approach each other. 



1340. Sometimes it is difficult to distinguish between a true fissure and a depression 

 in which was lodged a superficial vessel. Such vascular trenches, however, have usually 

 more abrupt and sharply denned edges than the fissures (Wilder, 11, 221). 



The mesal aspect of the hemisphere is largely a plane surface ; but the lateral and 

 other aspects present difficulties in respect to perspective which are common to convex 

 surfaces. Where a hemisphere is very peculiar, the drawings should be based upon pho- 

 tographs. The method of drawing fissures described by the senior author in 1873 (11, 

 219), in which the perspective was ignored, is no longer recommended by him. 



1341. Indicating the Relative Depth of Fissures. As appears in Fig. 122, and in PI. 

 Ill, Fig. 13, and PI. IV, Fig. 15, the fissures vary considerably in depth. They also vary 

 in different parts of their course, being usually deepest near the middle of their length. 

 Where a fissure is wholly superficial, it may be represented by a shading ; but otherwise 

 a line must be employed, the width of which may indicate the depth of the fissure in dif- 

 ferent parts of its extent and as compared with other fissures. The depth may be apcer 

 tained by carefully " sounding " with a graduated, thin, smooth and rounded rule, or by 

 sections of the brain after the location, extent and connection of the fissures have been 

 indicated by lines of uniform width. 



1342. Table of the Cerebral Fissures. The accompanying Table (p. 496) includes 

 an alphabetical list of the feline cerebral fissures, with the abbreviations employed in 

 this work, and the principal synonyms. 



The constant fissures are printed in black letter. 



The synonymy is limited to writers who have made special additions to the technical 

 nomenclature, and excludes those who have employed phrases or vernacular names, or 

 who have used the names of other writers in purely physiological papers. 



1343. Sources of the Names. The following brief statement respecting the names is 

 quoted from the senior author's paper (8, 50) : 



"Owen's ' postsylman ' should not be displaced by Krueg's ' suprasylmi posterior,' nor 

 Tn\s' marginal' by ' suprasplenialis.' Likewise, Flower's ' supraorUtal' has priority ever 

 my 'presylman' which Krueg has adopted [and is free from the implication of a doubt- 

 ful homology]. 



" On the other hand, Krueg's 'anterior' and ' postica' are so much more usable than 

 previous names as to be worthy of acceptance, especially as they may be regarded as 

 abbreviations of the phrases by which the fissures in question were designated by Owen 

 and myself. ' Splenialis ' is to be preferred to supercallosal or calloso-marginalis^ so long 

 as the human homologue of the fissure is uncertain. If marginalis is to be retained, post- 

 mar ginalis will be better than ' postsplenialis.' 



" I am particularly gratified to find that Krueg admits as fissural integers the ansata 

 and the diagonalis ; the former I had intended to call transversa and the latter intermedia, 

 but Krueg's names must be retained. We agree also in regarding Owen's ' medilaleral' 

 as composed of two fissures, which Krueg terms medilateral and confinis. I had intended 

 to leave Owen's name attached to the fissure which is really mesad of the lateralis and to 

 call the [caudal] curved division lunata ; the name lunata has now been given to what 

 otherwise would have been sublunata. I have applied the name intermedia to a fissure 

 which Krueg mentions but does not name. " 



