LECTURE VI. 169 



command I have measm'ed M. Wagner^s delineations. I have, 

 in the engraved brains of a microcephalus and a chimpanzee^ 

 measured two distances on the left side — the first from the 

 apex of the brain to the vertical fissure which separates the 

 posterior lobe, the second from the above fissure to the end of 

 the posterior lobe. I find for these measures, in the chim- 

 panzee : length of the anterior lobe = 76 milhmetres ; of the 

 posterior lobe = 21 millimetres; — in the microcephalus : length 

 of anterior lobe = 75 millimetres ; of the posterior lobe = 20 

 millimetres. I further find from Wagner's measurements of 

 the cerebral surface, that it is to the surface of the posterior 

 lobe: mean in eight males = 100 : 16"2; that, on the con- 

 trary, in the microcephalus, the proportion is = 100 : 68'5 ; 

 that, therefore, the posterior lobe presents a surface four times 

 greater in the microcephalus than in the adult man ; that, 

 therefore, the idiot has a posterior lobe at least as much deve- 

 loped as the ape. 



Result. — The posterior lobe is in the microcephalus just as 

 large as in the ape ; the idiot has in proportion to the cere- 

 brum exactly as large a posterior lobe as the chimpanzee. 

 The idiot has not the deep transversal fissure, nor the opercu- 

 lum of the chimpanzee, but no more has the devil's ape, and it 

 cannot be said that the human embryo could lapse into the 

 chimpanzee, whilst its posterior lobe resembles that of the 

 devil's ape as closely as one egg resembles another. Here, 

 therefore, the size and form of the posterior lobe is exactly as 

 in the ape ; the cerebrum, the anterior and posterior lobes, 

 have the simian type. 



The cerebellum is not quite in the same condition, as it pro- 

 jects behind. But this only results from its size, being less 

 arrested it approaches the normal human cerebellum, having 

 become too large in proportion to the arrested cerebrum. This 

 also can be shown by the measurements by Wagner of the 

 brains of four microcephali and an old orang. 



Meiin of the -1 Microcephiili. Orang. 



Length of cerebrum - - 110'25 - - 101 



Breadth of cerebrum - - 79'25 - - 108 



Breadth of cerebellum - 78-75 - - 86 



