308 MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 



position of the ascending ramus and a more or less concealed separating gyrus can 

 always be found. This is the case in the brain of a Chinaman, Plate XLI, figs. 3 

 and 4, and also in the brain, Plate XLIII, fig. 2. Its ordinary aspect is seen in 

 fig. 1, Plate XLIII. Huxley says that it opens into the supero-frontal sulcus, a 

 statement which Ecker regards as probably a slip of the pen. Possibly, however, 

 another fissure, f 4 , Plate XLII, fig. 1, which is a vertical branch of the superior 

 frontal, may have been inadvertently mentioned, and this might readily occur. 

 This fissure, f 4 , is very differently developed in different brains; sometimes, as in 

 the figure indicated, being almost as well marked as the central itself, and in 

 others, Plate XLI, fig. 3, being quite feebly developed. It seems to be related 

 inversely to the extent of development of f 3 , being long when this is short and 

 vice versa. Although it is thus as well marked in the human brain as the prsecen- 

 trals, f 3 , and in many cases even more largely developed, it does not seem to have 

 attracted the special notice of previous writers. Ecker does not even mention it. 

 I think it probable that when largely developed, as in Plate XLII, fig. 1, or Plate 

 XLIV, fig. 1, it has been confused with the vertical lower frontal or prsecentralis, 

 f 3 , instead of recognizing its true character as a vertical prolongation downward 

 of the superior frontal fissure. I propose for it, therefore, the name of the vertical 

 sulcus of the superior frontal, sulcus frontalis verticalis superior. We must 

 remember, however, that they are not distinct and separate fissures from a mor- 

 phological standpoint, comparable in value to the frontals themselves, although 

 sometimes they become separated from the horizontal part by small bridging gyri, 

 and then take on apparently the appearance of individual fissures. The varying 

 degrees of development of these two sulci may be well seen by comparing Plate 

 XLIII, fig. 2, with Plate XLIV, fig. 1. Gratiolet does not name or distinguish 

 either of these fissures in Man. He describes, however, the inferior vertical frontal 

 in the brain of Cercopitkecus, and has figured it as existing in the human brain. 

 In the simian brain the inferior vertical frontal is usually well marked, 

 but the superior is not found in most of them, owing to the slight and irregular 

 development of the superior frontal fissure. It may be seen, however, indicated 

 in the brains of Cynocephalus and Ateles, Plate XXXVIII, fig. 3, and Plate XXXVII, 

 fig. 15, (in the descending portion off 1 ) whilst in the Chimpanzee, Plate XXXVIII, 

 fig. 13, f 4 , and Plate XXXIX, fig. 4, f 4 , it approaches the human type. 



The convolution, A C, lying directly in front of the central fissure and con- 

 tained between it and the two vertical frontals, is the anterior central convolution 

 of Huschke and Ecker, anterior parietal gyrus of Huxley ■, premier pli ascendant of 

 Gratiolet, and ascending frontal gyrus of Turner. This convolution is constant in 

 its appearance, depending as it does upon the development of the central fissure, 

 and is continuous as a rule both above and below with the posterior central convo- 

 lution, P C ; but, as we pointed out previously, in a certain number of cases it is 

 separated from the posterior central by the fissura centralis becoming confluent 

 with the Sylvian. In front it unites with the three frontal convolutions. 



These lateral convolutions of the frontal region can generally be distinguished 



