344 DEVELOPMENT OF THE HUMAN BRAIN 



terior extension of the * fissure of the Hippocampus,' which 

 appears ahout the same time, and is a marking constantly 

 present, even in lower Vertebrates, on the inner side of 

 the brain. Gratiolet indeed believes that this latter fissure 

 is the first to appear on the inner side of the hemisphere. 

 Kather later the ' parallel fissure ' of the Temporal Lobe 

 becomes distinguishable, and, as above stated, by the 

 beginning of the seventh month, the other principal fis- 

 sures of the brain have made their appearance. 



Probably Ecker is correct in his view that the precise 

 time at which the principal ' fissures ' appear, as well as their 

 exact order of appearance, is subject to some variation in 

 different individuals. Both he and Huxley consider there 

 is no evidence to show that the fissures of the brain of a 

 Chimpanzee or of an Orang do not appear in essentially 

 the same order as those of the Human Infant, notwith- 

 standing the opinion expressed by Gratiolet to the effect 

 that there are certain slight differences. 



At the time of birth the development of the convolutions 

 is so complete in the Human Infant that they differ from 

 those of the adult, only by presenting a little less of com- 

 plication in regard to minor details. 



During the attainment of this degree of convolutional 

 complexity, however, some important changes have been 

 taking place in the relative development of the different 

 * Lobes ' of the brain. At the seventh month the Parietal 

 Lobe is notably small,* and apparently as a consequence 

 of this the ' fissure of Kolando ' is bent nearly at right 

 angles, just as it is in the brains of the adult Orang and 

 to a less extent in that of the Chimpanzee. At this same 

 period the Frontal Lobe is large, and so also is the 

 Temporal Lobe, though its convolutions are still very 

 imperfectly marked out. The length of the Temporal 

 . . * See Gratiolet's " Anat. Comp. du Syst. Nerv.," PI. xxxi, fig. 1. 



