164 LECTURE vr. 



Prof. Wagner finds sucli an organ — with Gratiolet. " The 

 superior apes approach, man gradually as regards richness of con- 

 volution, depth of fissures, and the presence of the gyri breves 

 in the central lobe of the island, and greater asymmetry , etc. 

 But they are far behind man as regards the preponderance of 

 the large hemispheres, especially as regards their proportions 

 to the cerebellum ; and there are distinctive differences in the 

 arrangement, size, and limitation of the posterior lobes, which 

 are always more developed in the ape and cover a portion of 

 the convolutions, which Gratiolet terms plis de passage (trans- 

 ition lobes) ." In a note to this, Wagner observes, " The 

 posterior lobes of the apes do not admit of a strict reduction of 

 their convolutions to man. That I have done so by way of essay 

 in my tables, and have paid no particular attention to Gratiolet' s 

 plis de passage, was done in order to establish a more simple 

 terminology, which may be useful in cerebral dissections." 



I have distinguished some of the above words by itahcs to 

 show how contradictory they are. First, it is said, the poste- 

 rior lobes have a remarkable resemblance, then they exhibit a • 

 striking difference ; and how ? The only human character 

 which Wagner is able to find, the cap-like covering of the 

 transition convolutions, he estimates so little as to omit it 

 altogether, simply for the sake of the terminology in dissections. 



Let us now return to Gratiolet, from whom the facts are bor- 

 rowed. " The shape, says this author, of the brain is known. 

 Its elevation, the breadth of the frontal lobe, the anterior 

 portion of which, instead of becoming pointed, is formed by a 

 surface which corresponds to the expansion of the frontal bone. 

 The depression of the Sylvian fissure, the richness and com- 

 plication of the secondary convolutions distinguish at first 

 sight the human from the simian brain. 



" Yet in spite of these differences, however great and charac- 

 teristic they may be, when we compare the proportions of the 

 individual parts, there still remain between the human and 

 the simian brain such analogies that a general description is 

 sufficient for both." 



Further on he says, " This is an essential character ; in man 

 all transition convolutions are superficial." This fact is signi- 



