276 



MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 



The monkeys and apes have also been arranged as follows : — 



Family I. SIMIAD.E! 

 Sub-Families 



Family II. CEBID^E 

 Sub-Families 



' 1. Simiinse 



2. Semnopithecinse 

 „ 3. Cynopithecinse 



1. Cebinae 



2. Myeetinse 



3. Pithecinee 



4. ISTyctipithecinse 



5. Hapalinae 



Genera. 



Simia 



Troglodytes 

 Hylobates 

 f Semnopithecus 



[ COEOBUS 



Cercopithecus 



Macacus 



Cynocephalus 

 f Ateles 

 I Eriodes 

 I Lagothrix 

 [ Cebus 



Mycetes 



f PlTHECIA 



t Brachyurus 

 Nyctipithecus 

 Chrysothrix 

 Callithrix 



f Hapale 



[ Midas 



The mistake is often made by those studying the fissures and convolutions 

 of other orders of mammalia, of attempting to compare their convolutional charac- 

 ters with those of the Primates, including Man. These mistakes have been made 

 not so much by comparative anatomists as by physiologists in attempting to trans- 

 fer to the case of Man experiments made upon the lower animals in respect to cere- 

 bral localization. From all the evidence at our command the Primates are only 

 closely related to the group of the discoidal placental mammals, a group which 

 includes, besides the Primates, the orders Rodentia, Insectivora and Chiroptera. 

 Thus, the genetic affiliation of the Primates with the other existing mammalian 

 orders must have been through an almost smooth-brained ancestor, and as a con- 

 sequence of this the fissuration of the primate brain must be studied as a type 

 of itself. We cannot expect, nor do we find any exact homological relations 

 between the convolutions of this phyllum and those of the other mammalian 

 phylla possessing convoluted brains, which formerly were grouped together by 

 Owen under the name of the Gyrencephala. 



MORPHOLOGY. 

 From the preceding historical and general survey, it will be seen that the sub- 

 ject of convolutional morphology is a highly complex one and the difficulties have 

 been greatly increased by the various, and in many cases unsuitable, nomenclature 

 that has at different periods been applied to the numerous gyres, lobules, fissures 

 and sulci of the cerebral surface. Evidently there must be certain morphological 

 laws or principles upon which the production of fissures and convolutions depends, 

 and if it be possible to discover those laws, it will undoubtedly give rise to a simpler 

 and more methodical system of naming the different parts of the great brain 

 surface. We have already seen that Huschke, Bischoff and Pansch have each at- 

 tempted to formulate such a plan; but to all of these the writer believes there are 

 certain fundamental objections, the nature of which will be pointed out in the fol- 

 lowing pages. 



