CiiAF. XXIII.] OF THE HUMAN BRAIN. 451 



since the nerve elements of this region are represented by 

 a single stratum of pyramidal cells, which differ also only 

 in size from the so-called ' giant cells ' of the parietal or 

 frontal Convolutions. 



There is in fact, in the writer's opinion, no valid reason 

 for supposing, as many do, that these ' giant-cells ' differ 

 at all in kind from others of smaller and smaller size with 

 which they are intermixed, or which, in the corresponding 

 layer, alone exist in so very many of the convolutions of 

 the Cerebrum. 



Similar kinds of cell elements to those found in the Convolutions 

 of the Human Brain, and similarly arranged, are to be found in 

 the Convolutions of Apes and Monkeys. 



In lower animals the greatest portion of the Cortex is also six- 

 laminated, but in certain special and limited (thoigh varying) 

 regions in each kind, a five-laminated Cortex exists. These laminoB, 

 according to Bevan Lewis, are also, to a considerable extent, iden- 

 tical in composition, though the first (which is, in the main, a mere 

 connective tissue layer) has generally a greater comparative depth 

 in the Sheep, the Pig, and other lower animals, than in Man. He 

 says: — " It is in the essential character of the individual cells of 

 these layers, in the relationship of these anatomical units the one 

 to the other, and in their general distribution, that we detect diver- 

 gence from the type normal to the higher Mammalia." 



In Man, the Ape, the Cat, and the Ocelot, the ' giant ' cells are 

 swollen and more rounded (owing to their giving ofi' a larger num- 

 ber of processes), than in such animals as the Sheep and the Pig. 

 In the latter these cells are more simply pyramidal, and have a 

 smaller number of inter-connecting processes. Such cells are, 

 moreover, scattered over a wide area. But in the Cat and otl^er 

 Carnivora, the area in which the * giant ' cells are found is very 

 restricted — much more so than in Man and the Quadrumana,. 



Again, according to Bevan Lewis, a peculiar kind of ' globose * 

 cell with few connecting processes, is to be found amidst the other 

 elements in the second and third layers of the Pig and Sheep, and 

 also in Apes — though such elements have been met with in Man 

 only in the brains of Idiots or Imbeciles. 



