CEREERAL CONVOLUTIONS " SALLY." 59 



20)^ having a course more nearly parallel with the Rolando 

 than is the case in " Sally's " brain. In both of Cunningham's 

 figures (pp. 203, 204) this furrow continues the direction of 

 the inferior postcen trails {p^.). 



Cunningham states (p. 230) that the union of superior post- 

 centralis (/j2,) with inferior is the usual condition in chim- 

 panzee ; and finds them separated in only two of the brains 

 out of eight examined, and that only on one side. In "Sally," 

 in Miiller's chimpanzee, and two others from the Royal College 

 of Surgeons, as well as in Herdman's, I find the fissure marked 

 by Cunningham as upper part of superior postcentralis, 

 separate from the rest of the system, and in all these instances 

 it loses its parallelism to Rolando, becomes more or less oblique, 

 and enters into connection with the furrow ps. (secondary 

 sulcus of sup. par. lobule). 



6. The Region of the Affenspalte. 



The most interesting feature in '' Sally's " brain, however, is 

 the condition of the hinder end of the intra-parietal fissure. 



In the normal chimpanzee brain, and in the lower apes, 

 the hinder part of the parietal lobe is overlapped by a com- 

 paratively thin fold of the occipital lobe, known as the 

 " occipital operculum." This lies flat against the parietal 

 lobe, and thus conceals a greater or less amount of the latter. 

 The deep cleft, extending nearly directly backwards and slightly 

 downwards, existing between the operculum and the parietal 

 lobe, is known as the '' Affenspalte," or Simian fissure (figs. 27, 

 29, show its direction well). But some confusion has resulted 

 from the application of this term to the superficial groove 

 between the edge of the operculum and the parietal lobe. 

 This superficial groove has also wrongly been termed the 

 " external parieto-occipital " fissure, since it is apparently 

 continuous with the " internal " fissure of that name. The 

 true " Afi'enspalte " lies behind this latter fissure, and the two 

 are independent. 



The parieto-occipital fissure is a vertically placed fissure in 

 the median surface of the hemisphere, into which it extends 



