346 MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 



The nomenclature as derived from the morphological views advanced in this 

 paper will be seen to be exceedingly simple. It forms a connected and systematic 

 whole; whilst, at the same time, the various synonyms can be readily compared 

 with it. 



CEREBRAL CONVOLUTIONS OF THE CARNIVORA, UNGULATA, ETC. 



Thus far we have considered only the convolutional configuration of the cerebral 

 surfaces of the Primates. We now propose to review in a brief way some of the conclu- 

 sions derived from a study of the convolutions and fissures as they are found in some 

 of the other orders of mammalia. We shall be compelled to confine ourselves to 

 pointing out merety the general results attained, without entering into the details, 

 which, although they have proved interesting, would prolong this dissertation to 

 an unreasonable length. I have, however, found that the general arrangement of 

 the fissures and convolutions in these animals indicates the action of the same general 

 laws that govern their formation in the Primates. The absence of an occipital lobe 

 reduces the complexity of the relations and as a result, whilst many of these 

 animals possess brains even more highly convoluted than in Man, the type or plan 

 upon which they are built is of a much simple rcharacter, bringing into play the 

 principle of vegetative repetition to account for their origin and numbers. All are 

 constructed upon a fundamental morphological type and this type is a regular 

 and symmetrical one. The conditions of growth, owing to simpler and simi- 

 lar relations, produce types that are more nearly related to each other, as a 

 rule, than they are to the structure of the convolutional conformation of the 

 Primates. The development of the occipital lobe and the enormous relative growth 

 of the fronto-parietal region produce in the latter animals a type which even in its 

 moderately developed condition stamps it as sui generis. 



We have at various times expressed the opinion that many of the sulci and 

 sulculi of the brain are only repetitions of lines of fissuration already formed, due 

 to prolonged action of the same dynamical conditions. In studying the brains of 

 the Carnivora, Ungulata, etc., this relation is specially prominent and it appears to 

 me that many of the fissures found in these brains must be regarded in this light, 

 that is, as vegetative repetitions. Viewed in this way many of the difficulties in 

 regard to the identification of homologous fissures in different brains disappear. 

 According to the mechanical theory a deep and distinct fissure having been formed, 

 after reaching its limit of depth, there would be a tendency to produce other fissures 

 following the same general direction, having the same general appearance and 

 depending for their formation on the one originally laid down. According to the 

 view that fissures are the result of retarded cerebral growth, we may expect to find, 

 especially in lower forms of brains in which much fissuration exists, vegetative 

 repetitions of the same lines of growth. In either case the fissures which appear 

 after the original fissure, and which follow its general contour, should be considered 

 as belonging to one group with that fissure, and to be of secondary importance in 

 relation to it. Hence in many cases, instead of seeking fissures separately homolo- 



