196 On the Structure of the Brain in Man and Monkeys. 



the parietal and occipital lobes are most so. The central lobe- 

 insula Reilii— with its gyrations appears to be wanting or very 

 rudimentary in the lower niicrocephals as is also the operculum 

 (Klappdeckel), while all of these are present in the orang. 



4. Though the gyri are smaller, stunted or wanting, and the 

 gray layer is thinner in the brains of microcephals, yet so far as 

 the gyn are present they show the same relation and order as in 

 the normal human brain. This normal arrangement, so far as I 

 may judge from casts of the hollows of skulls and from a few 

 dissections, is the same in type for all races of men. 



5. The lateral ventricle appears relatively larger in the micro- 

 cephal, and this shows that there is an early arrest of develop- 

 ment, usually occurring in the third or fourth month, at which 

 time the parietal and occipital lobes begin to grow, the central 

 lobe IS still rudimentary and the frontal and temporal lobes, 

 especially the latter, have quite a development. The embryonal 

 condition of some bones of the skull confirms this view.' But 

 this arrest is not so much arrest of growth as of development, 

 the gyn and lobes increasing slowly in size and the atrophy or 

 limitation being mostly shown in those parts that are undevel- 

 oped at the time of the arrest. 



6. The resemblance to the brain of apes and particularly to 

 that of the chimpanzee is only apparent, and consists mainly in 

 the lesser size of the gyri and their consequent symmetrv, while 

 tundamental points, as the greater development of the ^cipital 

 Jobe, the posterior occipital fissure, &c., show distinctive ground 

 plans for the two orders, Bimana and Quadrumana. 



7 I he condition of the bone tissue, the occasional asymmetry 

 of the skull, the welding of the sutures, make it probable that 

 in such cases a primitive disease of the bone tissue or rather of 

 the whole nutritive system plays a part, as H. Miiller has shown 

 m foetel r^ch\t\s.~.{WUrbvrg Medic. Zeits., 1860.) 



8. The anatomical condition of the microcephalous brain-- 

 see above— confirms the view that the cerebellum is not rela- 

 ted to the intelligence but to the motor faculties. For whilst 

 the intellect is extraordinarily wanting, the latter are hardly f 

 at all deficient. It is true microcephals usually learn to walk 

 late and have an uncertain or stumbling gait, but they are often 

 quick and nimble in climbing. The complete integrity of the 

 senses, especially of sight and hearing, favors the view that 

 the transformation of sensations into perceptions, (YorstelluPgen 

 takes place in the interior elements of the brain, in the basal 

 part of the cerebrum, rather than in any part of the superfi- 

 cial layer which may exist in the frontal and temporal lobes. 



ihe relation between the cerebrum and the intelligence is ^ 

 express that we may say it is a certain amount of develop- 

 ment of the former that is followed by the distinctive humaa 



