220 JoURxN'AL OK CoMi'A K ATI VE NeUKOLOGV. 



and passes caudo-mesad. By these two fissures there are 

 defined a large mesaxial lobe me&ad of the frontal fissure and 

 a narrow occipital lobe caudad of the occipital fissure. The 

 fourth important fissure is the Sylvian, which is not so 

 strongly developed as the preceding. It arises on the ventral 

 surface in the centre of the lateral aspect and passes dorsad. 

 This fissure, with the occipital, defines a triangular lobe, with 

 the apex directed ventrad, the cuneate lobe. Behind the 

 cuneate and ventrad of the occipital lobe, from which it is 

 separated by a small fissure, is a large lobe which may be 

 called the temporal lobe, though in the cat fish it occupies 

 the caudo-ventral end of the cerebrum. The term hippo- 

 campal lobe is applied to the lip, or ventral extrusion, just 

 laterad of the sinus rhinalis. Cephalad there is another 

 small fissure which may be considered as a part of the 

 rhinalis. It arises from the lateral edge of the radix lateralis, 

 passes dorsad and, with the frontal fissure, circumscribes a 

 frontal lobe. This lobe lies immediately dorsad of the olfac- 

 tory crus and is very small. There is still another noteworthy 

 fissure in the median sinus between the two basal lobes. It 

 runs in each lobe longitudinally in both directions from the 

 anterior commissure, It is best observed in transection. 

 There are are other small fissures on the dorsal surface, but 

 they seem not to be constant and are considered unimportant. 

 It is to be remembered that all of these fissures, except the 

 rhinalis and possibly the Sylvian, are spurious fissures and are 

 not to be homologized with the cerebral fissures of higher 

 animals. That is, they are fissures of the axial lobe, not of 

 the cortex, for this dorsal surface is a ventricular surface and 

 is clothed with epithelium, like the pallium. The epi- 

 thelium here, however, tends to be more columnar than that 

 of the pallium. 



To understand the full significance of these lobes it will 

 be necessary to examine the cellular histology of the cerebrum 

 in some detail. A transection cephalad to the anterior 

 commissure reveals three areas sharply differentiated histo- 



