MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 347 



gous to each other, we will be obliged to consider certain groups to be homologous 

 to certain other groups, the number of separate fissures of which may be more or 

 less numerous. Owen, in founding his nomenclature of the cerebral fissures in the 

 Carnivora and Ungulata, gave a distinct and separate name to each fissure, and he 

 endeavored to point out the homologue of each of these in different brains. If, how- 

 ever, we are to regard that at least some of the fissures are entirely secondary and 

 to be considered merely as vegetative repetitions, then we must not expect to seek, 

 nor is it possible to find, homologues for each separate fissure even in closely 

 related brains. This view of the subject of cerebral fissuration is important in con- 

 nection with the question of new fissural integers to which Wilder has given much 

 attention. 



We shall first consider the arrangement of the fissures and convolutions as 

 found in the brain of the Carnivora, and for this purpose we shall take as a type 

 of these relations the brains of the ocelot, lion, leopard and domestic cat, Plate XLV, 

 figs. 6, 7, 14, 15, 16, 17, 18 and 19. 



The fissure of Sylvius is represented by a well-marked fissure, s s, which 

 separates the lateral inferior portion into two distinct parts which might be termed 

 the parieto-frontal and parieto-temporal lobes. The posterior horn of the ventricle 

 not being developed there is no distinct occipital lobe, and the cerebral hemisphere 

 is confined to the region covered by the parietal bone. The convolutions are 

 arranged in their least modified condition in the form of four horse-shoe-like arches 

 surrounding the upper end of the Sylvian fissure, and separated by three lateral 

 arched fissures, Plate XLV, fig. 1. In many forms the first arched fissure immedi- 

 ately surrounding the calcarine is broken in two portions, the connecting arched 

 portion being absent. These have been termed respectively (Krueg, Wilder) the 

 fissura anterior, fa, and the fissura postica, f p, Plate XLV, figs. 6, 10, 16, 19 and 

 21. 



The second or middle arched fissure following the same writers is the fissura 

 supersylviana, s s, its posterior portion being termed the postsylviana, p s. The 

 third or upper arch is known as the fissura lateralis, 1, its posterior portion as the 

 fissura medilateralis, ml. A deep transverse cleft is formed upon the frontal lobe, 

 extending from the position of the fissura longitudinalis transversely outward. It is 

 the extremity of one of the mesial fissures, and is known as the fissura cruciata, c r. 

 A transverse fissure which is often connected with the fissura lateralis is called the 

 ansate fissure, a n, whilst a fissure which in many cases arches around the fissura 

 cruciata is known as the coronal, cor. The arrangement of these fissures varies 

 considerably in different genera and species, according to their relative length and 

 degree of development. Running antero-posteriorly near the lower border of the 

 hemisphere we have a deep and well-marked furrow, the fissura rhinalis, r h, the 

 posterior portion of which is known under the name of the fissura postrhinalis, p r h. 

 Other fissures are the superorbitalis, s o, and the diagonalis, d g. 



On the mesial surface of the brain, Plate XLV, figs. 3, 8, 17, 18 and 20, we 

 find situated posteriorly a more or less wedge-shaped lobule, P, from which are di- 



