310 MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 



however, distinguishes but two, and I believe he correctly considers this region. 

 Three distinct and separate convolutions of morphological value cannot be sepa- 

 rated. The three generally described by authors are the posterior central, P C, 

 the superior parietal, S P 1 , and the inferior parietal, I P 2 . Pansch considers the 

 convolution, S P ! + P C, that is, the posterior central plus the superior parietal of 

 other writers, as a single convolution, and calls it the gyrus parietalis superior, 

 while I P 2 or P 2 P 2 , he terms the gyrus parietalis inferior, separated from each 

 other by the fissure, i p, the interparietal of Turner. With this method of con- 

 sidering the parietal region I entirely agree. Evidently, as may be seen by refer- 

 ring to any of the plates, the convolution back of the central fissure, P C, is not 

 distinct from the portion marked P 1 , but is directly continuous with it. Recog- 

 nized in this way, the structure of the lateral parietal surface can be easily under- 

 stood, whilst viewed in the manner usual with most writers, that is, dividing it up 

 into a number of separate lobules without pointing out their morphological relations, 

 it becomes very difficult to understand. I will first briefly direct attention to how 

 it is regarded by previous investigators, and will then point out what appears to 

 me to be its true structure. In the first place there has been distinguished a 

 separate convolution, P C. Ecker calls this the posterior central convolution, 

 deuxieme pli ascendant of Gratiolet ; the ascending parietal of Turner; posterior 

 parietal gyrus of Huxley. The portion, S P 1 , is called by Ecker the lobulus 

 parietalis superior, the lobule du deuxieme pli ascendant of Gratiolet, the posterior 

 parietal lobule of Huxley, Turner and other English authors. With regard to the 

 convolution, I P, or P 2 P2 1 , still greater confusion exists. Pansch and Ecker give 

 to this convolution as a whole a distinct name. Pansch terms it the gyrus parie- 

 talis inferior and Ecker lobulus parietalis inferior. These names appear to me to 

 be correct although I object to the term lobule of Ecker. This convolution, espe- 

 cially in the negro, is as distinct and well marked as any of the frontal convolutions, 

 and if this does not satisfy us of its typical nature its appearance as presented in 

 the Simiadae certainly should. In them it constitutes one of the best marked con- 

 volutions of the hemisphere, far better marked than any of the frontals. The 

 portion P 2 Ecker calls the anterior division or lobulus supra-marginalis, and the 

 portion P2 1 he terms the posterior division or gyrus angularis. These correspond 

 with the parts called by Gratiolet the pli marginal superieur, P 2 , and the pli courbe 

 P2 1 . Wagner's division of this convolution adds still greater confusion. Thus he 

 calls the posterior division, P2 1 , the second parietal convolution, zweite oder mitt- 

 lere Scheitellappenwindung, and the anterior portion, P2 1 , the third parietal con- 

 volution, dritte Scheitellappenwindung . Bischoff, with his peculiar theory of the 

 manner of arrangement of the convolutions, calls the anterior portion, P 2 , erste 

 oder vordere Sckeitelbogenwindung, and the posterior, P2 l , zweite oder mittlere 

 Scheitelbogenwindung . This method of nomenclature seems to me to be not only 

 faulty but it absolutely obscures all idea of relation and connection in this region. 

 The convolution, P 2 P2 1 , is not two separate and distinct convolutions as this 

 division would lead us to suppose, but a single and distinct gyrus. Its individual 



