806 



PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



In the ruminants traces of the fissure of Rolando may be detected, 

 but in none of the ruminants, rodents, marsupials, or even carnivora, 

 with the exception of the seal, is there to be found a backward prolonga- 

 tion of the lateral ventricle forming a posterior cornu. 



In the quadrumana the plan of the arrangement of the cerebral con- 

 volutions to a certain extent resembles that seen in the cerebrum of man. 



The characteristics of this organization are found first, in the 

 existence of the occipital lobe, with the prolongation into it of the lateral 

 ventricle; second, the fissures occupy the position of the fissures of the 

 human brain, of which the most important are the fissure of Rolando, 

 dividing the frontal from the parietal lobe, the parieto-occipital fissure 



lens 

 al 



.id 



FIG. 348. MEDIAN ASPECT OF THE RIGHT HEMISPHERE. (Landois.) 



CC, corpus callosum divided longitudinally; Gf, gyrus fornicatus; H, gyrus hippocampi; 7;, sulc 

 hippocampi; U, unoinate gyrus ; cm, calloso-marginal fissure ; Fj, first frontal convolution; c, termir 

 portion of fissure of Rolando ; A, ascending frontal convolution ; B, ascending parietal convolution a: 

 paracentral lobule; Pi', praecuneus, or quadrate lobule ; Oz, cuneus ; Po, parieto-occipital fissure ; o, trans- 

 verse occipital fissure; oc, calcarine fissure; oct, superior, oclt, inferior ramus of the same; D, gyrus 

 descendens ; T 4 , gyrus occipito-temporalis lateralis (lobulua fusiformis) ; T 5 , gyms occipito-temporalis 

 medialis (lobus lingualis). 



distinguishing the occipital from the parietal lobe ; and, third, the fissure 

 of the hippocampi, formed by the folding inward of the cerebral substance 

 along the posterior cornua. In the higher monkeys numerous other 

 fissures complicate the cerebral surfaces and to a certain extent corre- 

 spond with the arrangement of the convolutions in the human brain.- 

 In all these may be recognized certain primary frontal, parietal, occipital, 

 and temporal convolutions, which have a general longitudinal direction. 

 As a rule, the cerebral hemispheres are more convoluted in the larger 

 species of any group of mammals than in the smaller species of the 

 same group. For example, in the pachydermata the highest degree of 

 complexity of the convolutions is found in the elephant. 



