300 Proceedings of the Royal Flujsical Society. 



have been frequently described, but no apology is needed for 

 referring to some of the principal features of my specimen, 

 siuce authorities are by no means agreed on several points, 

 and as the convolutions are undoubtedly subject to consider- 

 able variations, it is advisable that a number of cases should 

 be put on record in order that the average or typical condi- 

 tion may be determined. 



Sylvian Fissuee. — This fissure consists, as in the human 

 subject, of a main stem, with two branches or limbs. The 

 posterior limb is generally said to be more vertical than in 

 man, and this appears to be the case. According to Broca,^ 

 the anterior limb of the sylvian fissure in man constantly 

 divides into two branches, and in anthropoid apes this 

 division often occurs. Bischoff,^ on the other hand, holds 

 that two branches are rarely met with. In my specimen, it is 

 single, with a very faint trace of a forked arrangement at its 

 extremity. Miiller mentions a fissure placed in front of the 

 anterior limb of the sylvian fissure, which is sometimes mis- 

 taken for it. On raising the temporo- sphenoidal lobe, the latter 

 fissure will be found not to be continaous with the sylvian, 

 but to end on the under surface of the frontal lobe. I find a 

 fissure of this kind in my specimen. Through the kindness 

 of Sir Wm. Turner I had the opportunity of examining along 

 with him four chimpanzees' brains, which are in the Anatomi- 

 cal Museum of the University of Edinburgh. In all of them 

 the anterior limb of the sylvian fissure was single and short. 

 In some of them this was quite obvious, but in others it 

 appears to be continuous with the fissure, already referred to 

 as being in front of the sylvian. On raising the temporo- 

 sphenoidal lobe, however, the two were found to be separated 

 by a narrow bridging convolution. 



Fissure of FtOLANDO. — This fissure is very distinct in both 

 hemispheres of my specimen. It begins close to the great 

 longitudinal fissure, and runs downwards and forwards to end 

 a little above the posterior limb of the sylvian fissure. In its 

 course it is curved so as to form two anterior convexities of 



1 Memoirs ccrveaii de riionime et des [iriinates, Paris, 1SS8, p. 5S8. 



2 Sitzbericht dcr Miincheii Akad., Feb. 1871. 



