246 STUDY OF BRAINS OF SIX EMINENT SCIENTISTS AND SCHOLARS. 



The unusual dimensions of the callosum call for comment. The writer cannot 

 recall having ever before seen this structure of such great size as in the brain of Pro- 

 fessor J. Leidy. Its cross-section area is 10.606 sq. cm., neai'ly twice the average size. 

 Its great length, 8.5 cm., or 46.7 per cent, of the total hemicerebral length, is striking. 

 At the genu its thickness is 11 mm., the average thickness of the body is 9 mm., while 

 the maximum thickness of the splenium is 16.5 mm. It is the caudal part of the cal- 

 losum which is particularly massive, and that portion of the splenium which " rolls 

 under" (the " cauda corporis callosi " of Retzius and the splejiium proper of Beevor) 

 is certainly of unusual size. In the chapter on the comparison- of the brains of Pro- 

 fessor Cope and J. Leidy, these features will be discussed in detail. 



Left Hemicerebrum. The Interlobar Fissures. The Sylvian -Fissure and its 

 Rami. — The length of the sylvian from its presylvian junction to the episylvian is 

 6.3 cm. Its course is moderately sinuous and its walls are in close apposition. Its 

 angle with the plane passing through the ventral margins of the frontal and occipital 

 poles is 29°. Its depth at the presylvian point is 13 mm. ; medisylvian 18 mm. ; 

 postsylvian, 27 mm. The presylvian ramus is 1.1 cm. in length and springs from the 

 sylvian much further caudad than on the right side, and more so than in most brains. 

 The sub.sylvian ramus is short but well marked, and anastomoses cephalad with an 

 independent segment (possibly of the orbito-frontal). 



The basisylvian, measured from the tip of the temporal lobe is 20-21 mm. in 

 depth. Caudad the sylvian terminates in a short (7 mm.) episylvian ramus. There 

 is no hyposylvian. 



The Central Fissure. — The length of the central on this side is 10.3 cm., a trifle 

 longer than that of the right, as well as much more sinuous an^ more ramified. It 

 anastomoses cephalad with the supercentral and caudad with the subcentral. The 

 general direction of the fissure makes an angle of about 60° with the intercerebral 

 cleft. 



The Occipital Fissure. — The length on the meson is 3.5 cm. ; on the convex sur- 

 face 1.3 cm. At a point 1.3 cm. distant from the occipito-calcarine junction, the fis- 

 sure is joined by an unusually long and well-marked adoccipital, giving rise to an ap- 

 parent bifurcation of the occipital, not infrequently noted in some other brains.* The 

 fissure makes an angle of about 50° with tiie (arbitrary) horizontal plane chosen in 

 these studies, an extreme opposite to the very much greater angle described by this 

 fissure in the brain of Professor Cope. In Leidy's case this caudal deviation of the 

 fissure is due to the interpolation of a well-marked cuncolus, i. e., the wedge-shaped 

 piece marked off by the adoccipital. 



* In the brain of Dr. Coudereau there was an apparent trifnrcation of the occipital. 



