96 



THE VOYAGE OF H.M.S. CHALLENGES. 



3rd, and 4th parietal convolutions. Ferrier called them the 1st, 2nd, 3rd, and 4th 

 external convolutions, but he numbered them in the opposite direction from Leuret and 

 Broca, the first being next the longitudinal fissure whilst the fourth bounded the Sylvian 

 fissure. Owen preferred the following descriptive terms from above downwards — medial, 

 medilateral, supersylvian, and Sylvian folds or convolutions. Pansch named them from 

 above downwards — marginal, suprasylvian, outer Sylvian, inner Sylvian ; whdst Langley 

 called them from above downwards — superior, suprasylvian, ectosylvian, and Sylvian. 



If numerical terms are employed, then I thiuk the plan pursued by Ferrier of number- 

 ing the convolutions from above downwards is to be preferred to that of Leuret and 

 Broca, as the order of arrangement is thus brought into conformity with the numbering 

 of the convolutions of the frontal, occipital, and temporo-sphenoidal lobes in the human 

 brain, where in each lobe the highest convolution is the first. If on the other hand 

 descriptive terms are used, then I prefer Owen's name of suprasylvian for the convolution 

 immediately above the Sylvian convolution, instead of outer Sylvian or ectosylvian as 

 employed by Pansch and Langley ; whilst the highest convolution may appropriately be 

 called sagittal or marginal, and the one immediately below it mediolateral. Moreover, I 

 shall call the fissure which separates the Sylvian from the suprasylvian convolution 

 the suprasylvian fissure ; that between the suprasylvian and mediolateral convolutions 

 the lateral fissure ; whilst that between the mediolateral and marginal convolutions is the 

 mediolateral or sagittal fissure. On both the numerical and descriptive methods the 

 following terms are synonymous in brains with four tiers of convolutions : — 



1st external convolution 



1st curved fissure 



2nd external convolution 



2nd curved fissure 



3rd external convolution 



3rd curved fissure 



4th external convolution 



Sagittal or Marginal convolution. 

 Mediolateral or Sagittal fissure. 

 Mediolateral convolution. 

 Lateral fissure. 

 Suprasylvian convolution. 

 Suprasylvian fissure. 

 Sylvian convolution. 



Along with Flower and Ferrier I shall call the convolution which bounds the crucial 

 fissure in front, behind, and externally the sigmoid gyrus (sgc). 



The Sylvian and suprasylvian convolutions were bounded in front and below by 

 the jprsesylvian fissure (ps), Owen, 1 which passed forwards, upwards, and inwards to the 

 anterior part of the cerebrum, but did not reach the mesial longitudinal fissure. It 

 was separated from the triradiate fissure by the external supraorbital convolution, 

 and from the crucial fissure, above which its inner end was situated, by the sigmoid 

 convolution. Between the prassylvian and Sylvian fissures the anterior limbs of two 

 convolutions were situated, which were separated from each other by the suprasylvian 

 fissure. The more posterior and narrower of these two convolutions was the anterior 



1 Supraorbital fissure, Flower and Langley. 



