93 



The arcus is bounded by a sulcus which varies in depth and defi- 

 nition with the size of the gyrus which it limits. This last sulcus may 

 well be termed the sulcus para-cinguli. But this sulcus occupies a 

 position such that anastomosis with the superior post-central sulcus 

 is almost inevitable, and as a matter of fact such union occurs very 

 commonly indeed. The two furrows may be quite separate (Fig. 1. A.) 

 or more usually they become united. In this manner all sorts of 



Snl. centralis Sul. cingnli Sol. paracingnli 



, - Sul. pariet. 

 sup. 



Sul. par. horizon. 

 Sul. postcent. inf. 



Fig. 1 A. 



Sul. cinguli 

 Sul. centralis : Arcus cinguli 



Sul. postcent. 

 sup. 



. Fiss. par. occip. 



Sul. paroccipitalis 

 Sul. par sup. 

 Sul. par. horizontalis 



Sul. par. inf. 



Sul. postcent. inf. 



IB. 



Snl. cinguli Sul. cent. 

 Sul. pariet. sup. ' ^—«^V^ , ^rcus cinguli 



Arcus par. occ 



Sul. postcent. 

 sup. 



Sul. paracing. 



Sul. paroccip. 



Sulc. pariet. horiz. 



Sul. postcent. inf. 



Sul. centralis Sul. 

 cinguli 



Sul. postcent. sup. 

 Fiss. parieto. occ. 



SuL 



paroccip. 



Sul. pariet. sup. 

 Sul. pariet. horizon. 

 Sul. postcent. inf. 



Fig. 1 C. Fig. 1 D. 



Fig. 1. Varieties of furrow arrangements in the superior post-central field drawn 

 frown brains lately in my possession. All show the arcus cinguli very clearly, with 

 the sulcus paracinguli hounding it. In A the superior postcentral sulcus and the 

 sulcus paracinguli are quite separate, but in the remainder fusion has occurred. 



C is a variety open to various explanations (see text), and I am doubtful whether 

 sulcus parietalis superior may not really be absent in this case and therefore not 

 in the position to which I have assigned it. 



extraordinary shapes are produced. I have seen the sulcus cinguli 

 run directly into the superior post-central with but a slight shallow- 

 ing to mark their junction, though this is a rare condition (Fig. 1. D.). 



