STUDY OF BRAINS OP SIX EMINENT SCIENTISTS AND SCHOLARS. 247 



The Calcarine Fissure. — The calcarine and postcalcarine parts join to form a 

 simple uninterrupted fissure of quite sinuous course. Its total length is 6.2 cm. 



The occipital and calcarine fi.ssures meet at considerable depth and continue as 

 the occipito-calcarine stem, passing cephalad for 3 cm. to within 1 cm. of the hippo- 

 campal fissure. 



Fissures of the Frontal Lobe (Lateral Surface). The Precentral Fissural 

 Complex. — The supercentral fissure is of the usual zygal shape, anastomosing cephalad 

 directly with the superi'rontal and caudad with the central. Both the dorsal and ven- 

 tral limbs are long, so that the entire lateral extent of the fissure reaches 6.5 cm. 

 Separated from the supercentral by an isthmus is the tortuous and well-marked pre- 

 central fissure. The precentral dips into the sylvian cleft, while its cephalo-dorsal 

 ramus (Quain's "anterior precentral ramus") anastomoses with the medifrontal. 

 There is no transprecentral and no diagonal fissure on this half 



The superfrontal fissure is well-marked, extensive, and though quite ramified, 

 does not pursue a very tortuous course. It is 8.8 cm. in length, and runs fairly 

 parallel to the intercerebral cleft. Three paramesial segments mark the superfrontal 

 gyre, imperfectly dividing the convolution into two longitudinal tiers. In the pre- 

 frontal region there is a marked tendency to transverse fissuration. 



The medifrontal fissure, from its origin at the precentral ramus, passes cephalad 

 for 3 cm. to end in a Y-shaped manner. The fissure is a good example of the com- 

 pound zygal forms, the two zygons joining by a ramus and stipe respectively. 



Rather unusual appearances are presented by the subfrontal. The main (longi- 

 tudinal) portion is extremely short, terminating cephalad in an irregular radiate fissure, 

 while caudad it sends a long ramus toward the Sylvian, parallel with the radiate. 

 Dorsad it gives oif three short rami. The orbitofrontal may be traced as an irregular, 

 but fairly extensive fissure, in a part of its course resembling an additional medifrontal 

 segment. 



Mesial Surface. — The supercallosal sweeps cephalad uninterruptedly from its 

 junction with the paracentral for 12.5 cm., terminating just ventrad of the rostrum. 

 The paracentral is rather short and irregular ; its caudal limb is tortuous and anasto- 

 moses suj^erficially with the central fissure ; the cephalic limb is straight. There is 

 also an intraparacentral ramus. There is no inflected fissure. The frontomarginal 

 fissure is particularly well marked in this case ; except for a slight interruption just 

 cephalad of the genu, it attains a length of 11 cm., joining the rostral fissure cephalad. 

 The rostral fissure is 4.5 cm. in length ; a short subrostral is also present, anastomosing 

 with the olfactory fissure. The terminal hook of the supercallosal bears some resem- 

 blance to the transrostral of Retzius. 



A. p. S.— XXI. CC. 14, 10, '07. 



