18 ON THE AFFINITIES OF THE BRAIN 



them himself to carry; and anatomical investigation seems to me 

 hut to strengthen the argument based upon these literary con- 

 siderations. For this ' lobule of the marginal convolution ' is 

 very frequently asymmetrical on the two sides of the same brain, 

 and its development in any two human brains taken at hap- 

 hazard is pretty sure to present the very greatest differences. 

 Varying, as it does, most widely in absolute size, it varies also 

 in showing f rien de constant 1 ' in its relation to certain other 

 parts ; its value can hardly be high, therefore, as a serial charac- 

 teristic. 



The convolution numbered 4 in Fig. 1 and Fig. 3, the ' premier 

 pli ascendant ' of Gratiolet, is separated by a vertical more or less 

 interrupted fissure from the horizontal-lying frontal lobes % and 3. 

 Now, a line drawn down the long axis of this fissure would fall 

 a considerable way in front of the commencement of the fissure of 

 Sylvius. Such a line in the human brain falls always far behind 

 the commencement of that fissure, joining it, indeed, some way 

 behind the angle where the fissure of Sylvius makes its bend 

 horizontally backwards. The forward position of this line speaks 

 more strongly than can the vertical direction of the fissure of 

 Sylvius, of stunted antero-posterior growth of the frontal lobes, 

 and it deserves more attention than it has yet received. The 

 convolutions, No. 3, the superior frontal convolutions, are of all the 

 convolutions those in which by symmetry and simplicity, both 

 alike sure marks of degradation, the orang's brain contrasts to the 

 greatest disadvantage with man's. But this fourth and this fifth 

 point we shall leave to be elucidated by the reader for himself from 

 an examination of our figures. We will state, however, the details 

 which an examination of the chimpanzee's brain, instituted with a 

 view of seeing whether its convolutions were really more sym- 

 metrical and more simple than those of the orang, elicited, in con- 

 firmation of M. Gratiolet's views. In the orang, and in the 

 chimpanzee, both the frontal, 1, 2, 3, the 4 and 5 ascending pa- 

 rietal, and the superior bridging convolutions a, a, are asymmetrical 

 on the two sides of the brain. The occipital D, the temporo- 

 sphenoidal .8, and the convolutions b, b, b, named ' pli courbe ' by 

 M. Gratiolet, are symmetrical in the champanzee, but asymmetrical 

 in the orang. The occipital lobe is both more simple and more 



1 'Memoire,' 1. c. 



