1863.] 711 



bable ratios, in the two cases, of the weight of the encephalon, the 

 cerebrum, and the cerebellum to that of the body, and of the re- 

 lative weight of the cerebrum to the cerebellum. The result of this 

 inquiry is to prove that the entire encephalon was, in each case, 

 about one-fourth of its normal proportional weight. The cerebrum 

 was much more defective than the cerebellum. The idiot boy had 

 relatively more cerebellum, and the idiot woman more cerebrum. 



On studying the general form, dimensions, and relative position of 

 the parts of the encephalon, it appears that the entire brain in the 

 idiot woman resembled very closely, at first sight, both in its general 

 mass and in the form of its anterior part, the brain of the Chim- 

 panzee ; but a closer comparison shows great differences. The 

 cerebellum especially is of very great size, forming about one-fourth of 

 the entire mass, and, instead of being covered by the cerebrum, has 

 about '35 inch of it exposed posteriorly. 



A detailed description is then given of the fissures, lobes, and con- 

 volutions, which are compared with those of the healthy brain and 

 with those of the Chimpanzee. Only the most general conclusions 

 arrived at can here be given. 



Of the lobes, the temporal are remarkably large ; the parietal seem 

 to be next highly developed ; whilst the occipital and frontal are the 

 smallest. According to the author 



1. The idiots' cerebra are not merely diminutive organs, having 

 all the proper parts on a smaller scale, but these parts are fewer in 

 number, less complex, and different in relative proportion and 

 position. 



2. Nevertheless all the primary and connecting convolutions 

 proper to the human cerebrum are represented in the idiots, but 

 are very remarkably simplified. 



3. The degree to which the convolutions of those parts are de- 

 veloped follows the order observed in the lobes themselves. 



4. The convolutions of the idiot woman are more developed than 

 those of the idiot boy, except those of the parietal region. 



5. The peculiarities in the idiots' cerebra are due to arrest of de- 

 velopment occurring at some period of foetal existence. 



6. Judging from external appearances generally, it might be sup- 

 posed that this period was about the latter half of the seventh month, 

 and somewhat earlier in the boy than in the woman. But a closer 



