MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 261 



central convolution arching around the upper and lower extremities of the fissura 

 centralis. Posterior to those at the upper border of the hemisphere and extending 

 over to the mesial surface, are the superior internal parietal group of convolutions 

 [pbere innere Scheitelgruppe). Besides these he also calls attention to five so- 

 called arched parietal convolutions : — 



First. An anterior parietal arched convolution {erste oder vordere Scheitel- 

 bogenwindung) surrounding the upper extremity of the horizontal branch of the 

 fossa Sylvii. 



Second. A second or middle parietal arched convolution {zweite oder mittlere 

 ScJieitelbogentoindung) surrounding the upper extremity of the first temporal 

 fissure. 



Third. A third or posterior, surrounding the upper extremity of the second 

 temporal fissure. 



■ Fourth. A superior internal [pbere innere ScJieitelbogenwindung) , surround- 

 ing the upper extremity of the fissura perpendicularis interna. 



Fifth.. An inferior internal {tenter e innere ScJieitelbogenwindung) , surround- 

 ing the lower extremity of the fissura perpendicularis interna. 



On the occipital lobe he distinguishes three convolution groups: an outer upper, 

 the so-called cuneus, and two lower, an internal inferior or lobulus lingualis, and an 

 external inferior or lobulus fusiformis. In the temporal lobe Bischoff does not 

 differ to any marked degree from the nomenclature and boundaries of other writers. 



I have dwelt particularly on the results of the investigations of Huschke, 

 Pansch and Bischoff, as they are the only writers who have proposed any distinct 

 morphological plan or theory according to which the convolutions and fissures are 

 arranged in the Primates. With regard to the morphological plan given by Bis- 

 choff, I can but repeat the opinion of Ecker, " what Bischoff says is also perfectly 

 correct that a large number of the convolutions of the cerebral hemispheres are 

 arranged around the ends of the primary furrows in more or less simple or compli- 

 cated arches ; and it cannot be otherwise, for the ranges of mountains enclosing a 

 valley must necessarily pass into each other where the valley ends, but no special 

 explanation seems to be thereby disclosed." 



Pansch's division is founded, as he claims, on the areas divided off by important 

 fissures, those which appear the earliest in the human embryo; but these have no 

 definite connections either amongst themselves or with the plan of the cerebral 

 hemisphere, and do not, therefore, it appears to me, point out any type or plan. 

 Where Pansch failed was in not recognizing the fact that the fissures of the human 

 foetal brain do not represent the type, but only an abbreviation, of the Primate 

 brain, and this type or plan can only be determined by comparisons and corrections 

 made by a thorough analysis of all Primate brain forms, both in the adult condi- 

 tion and as far as material renders it possible with simian and especially lemurine 

 foetal brains. Only by such an extended survej^ will it be possible to thoroughly 

 accomplish this. The absence of such material, especially of foetal monkey brains, 

 renders the undertaking at the present time exceedingly difficult. 



