2]0 anatOmt of the centeal xeevous system. 



is what occurs. At present, moreover, we can even occasionally conclude from the 

 development of a definite cortical region the existence of an ability to execute in 

 a, certain direction. The elephant, for example, possesses an especially large cortical 

 field in the region of the cortex where the facial area is localized in the higher 

 mammals. This is entirely wanting in the rhinoceros and tapir. If nothing were 

 known of the wonderful ability of the animal to use its trunk in such various ways, 

 it might, however, be conjectured from the presence of the above-mentioned field in 

 the facial area that from this center muscles were innervated which were capable of 

 very special function. 



All the investigations on the mantle lead to the conclusion that it is 

 composed of separate areas, which may vary in relative size. One part of 

 these centers stands in relation to motor and sensory processes. Another 

 part, as yet studied in man only, contains, according to the brilliant dis- 

 covery of Fhchsig, association-regions alone which are well adapted struct- 

 urally to form connections with one another and with other centers. Ac- 

 cording to Fhchsig, it is probable that the intellectual superiority of the 

 Primates rests upon the high degree of perfection of the "centers of asso- 

 ciation." In point of fact, the brain-mantle generally increases in such a 

 manner that a larger mantle is found in the more intelligent animals than 

 in those especially deficient mentally and of low rank. It will be the object 

 of continued investigation to show how the individual elements grow. The 

 interest which investigations in the comparative anatomy of the cerebral 

 convolutions really have lies just in this inquiry, rather than in purely mor- 

 phological considerations. 



Very gradually, then, the mantle increases in extent ascending in the 

 vertebrate series. In the apes, belonging to the class of primates, it has 

 attained an expansion which borders closely on the relations found in man. 

 Nevertheless, an important factor, besides more unessential relations, still 

 separates it from the stage reached by man. The frontal lobe, still very 

 small in the lower apes, attains a large size in the higher apes, but always 

 remains very much inferior to that of man. In man, even, this develop- 

 mental process is in nowise terminated as yet. Differences still plainly 

 occur in the region of the frontal lobe which allow us to infer the possi- 

 bility of further perfecting. The inferior region of the frontal lobe, which 

 contains the centers of speech, and shows very marked variations in develop- 

 ment, is the part more particularly concerned. 



When a small mantle is present the fibers issuing from it can naturally 

 be only few in number. In fact, the radiation from the cortex is so meagre 

 in many smaller mammals that a real centrum semiovale is not formed at 

 all — the entire fiber-system more frequently being limited to a relatively 

 thin covering under the cortex. This layer of white matter then borders 

 directly upon the ventricle, and is traversed by the terminal filaments of 

 its epithelium. 



