142 



PROCEEDINGS OF THE ACADEMY OF 



[1881. 



Brain. — When the study of the structure of an animal is limited 

 to the investigation of its adult condition, without any reference 

 to its mode of development or regard to its natural affinities with 

 closely allied or even remote species, much will be found obscure, 

 or even entirely unintelligible in its organization. The study 

 of the brain is no exception to this general rule. Comparative 

 anatomy and embryology are, indeed, the lamps which throw light 

 upon the darkness of cerebral structure. Taking advantage of 

 the methods cultivated with such success bv Owen,^ Leuret- and 

 Gratiolet, Kreug,^ etc., let us begin our study of the brain of the 

 Hippopotamus by first considering, as suggested by Garrod,* so 

 far as is known, the general type of the artiodactyle brain, and 

 then ascertaining the amount of deviation from the type exhibited 

 in the brain of the different genera. Studied in this wa}', the brain 

 of the Hippopotamus will prove far more interesting and instruc- 

 tive than if merely described topographically. 



According to Kreug the simplest kind of ungulate brain is to 



be seen in the embryo of the Sheep, Ovis aries. Figs. 1, 2, 3, give 

 diagrammatically surface, side and mesial views of the hemisphere 

 of the same. On looking at the surface view (fig. 1), there will 

 be observed to the right of the great longitudinal fissure the 

 coronal fissure, co, anteriorly, and the lateral, I, posteriori}^, and 

 towards the side the supra-sylvian, ss, fissure with its anterior, 

 ascending, descending, and posterior branches. In addition to 

 these fissures may be seen upon the side view (fig. 2), the sylvian 

 fissure, sac, running transversely into the rhinal fissures, rh, 

 the diagonal, d, and the postica, p. The calloso marginal, sp, 



1 Com. Anati of Vertebrates, vol. iii, p. 115. 

 ^ Anatomie Comparee du Systeme Nerveux. 

 ^ Zeit. fiir wiss. Zoologie, Leipzig, 1878. Band 31. 

 * Op. cit., p. 12. 



