1879.] Comparative Structure of the Cortex Cerebri. 235 



of corresponding structures in certain members of the Ruminantia, 

 Carnivora, Quadrumana, and also in the human brain. For this pur- 

 pose the cerebrum was examined in the pig, sheep, cat, ocelot, and 

 Barbary ape. In all cases the hemispheres were sliced from end to 

 end in the fresh state upon the freezing microtone, and the sections 

 examined seriatim, both fresh and after preparation by a process 

 already described.* The regions to which special observation has 

 been directed, are those over which a five- and a six-laminated type of 

 cortex prevails, and which, in the members of the Ungulata examined, 

 include the upper arc of the great limbic lobe (gyrus fornicatus), the 

 frontal lobe, and the great mass of convolutions entering into the 

 formation of the parietal lobe. 



In this brief abstract I propose merely to enumerate the general 

 conclusions arrived at, and which may be stated as follows : — 



1st. In the Ungulata, as in higher Mammals, the cortex of the 

 brain exhibits an extensive six-laminated region and a less extensive 

 area constituted of five layers of nerve cells. These layers in the 

 six-laminated cortex consist, as in higher animals, of a peripheral 

 cortical layer, a second layer of small pyramidal cells, a third layer of 

 large pyramidal cells, a fourth of small pyramidal and angular 

 elements, succeeded by the large cells of the ganglionic series, and lastly 

 the layer of spindle cells. The divergencies observed in various groups 

 of animals are not dependent upon the general conformation and 

 constitution of these layers, so much as upon differences observed in 

 the essential characters of their elements and their mode of dis- 

 tribution. 



2nd. In the five-laminated type, the second band of small angular 

 and pyramidal cells is absent and the ganglionic layer assumes 

 characteristic features. 



3rd. Transition realms occur betwixt both laminated types in which 

 the special features characteristic of the ganglionic series are in direct 

 proportion to the thinning out and disappearance of the second band 

 of angular elements. 



4th. The ganglionic series in these members of the Ungulata differs 

 from that of higher Mammals in the conformation of its individual 

 elements and their distribution. 



As to Conformation. The cells are more elongated, pyramidal in con- 

 tour, and never assume the same average dimensions as those of 

 the cat, ocelot, and ape. The swollen plump cell of these animals is 

 never seen in the pig and sheep. 



As to Distribution. They are scattered over a comparatively far 

 wider area of the cortex. 



5th. The pyramidal form assumed by these cells is, from reasons 

 stated in the original paper, significant of far less complex relation - 

 * " Brain," a Journal of Neurology. Part iii. 1878. 



