A_Study of Cerebral Anthropology 25 



sidered in relation to the development of the entire cerebrum, and 

 consequently a measure of mentality. The ramus anterior ascen- 

 dens and ramus horizontalis of the fissura Sylvii were first 

 clearly explained in their developmental relation to the opercula 

 by Cunningham (1892). He found that the presence of both, 

 and widely separated, indicated that the operculum intermedium 

 is well developed ; consequently, in a study of the brain, opercular 

 development can be readily expressed in terms of the type of 

 arrangement of these rami. Eberstaller (1890) called attention 

 to the fact that distinction need not be made between the limbs as 

 to which was represented, when only one sulcus is present. He 

 found two limbs present in 45 per cent., Cunningham in 57.5 per 

 cent, and Retzius in 86 per cent. Smith (1903&) disagreed with 

 the above-quoted investigators in regard to the development of the 

 opercula and the rami anterior ascendens and horizontalis in that 

 " neither of the anterior limbs of the Sylvian fissure, as commonly 

 interpreted is a definite morphological feature for which an exact 

 homology can be found in another brain, . . . the ramus horizon- 

 talis is merely the anterior end of the sulcus suprasylvius, and its 

 upper lip is what I shall call the dorsal operculum." " In a cer- 

 tain number of these cases the so-called ramus ascendens is sec- 

 ondarily formed by the bending down of the anterior part 

 (operculum frontale of Cunningham or intermedium of Retzius) 

 of the dorsal operculum (mihi) ; this produces a kink in front 

 of Eberstaller's diagonal sulcus, and this kink is the ' ramus ascen- 

 dens.' " He also concludes that when a single ramus is present, it 

 is the representative of the " ramus horizontalis " of most authors. 

 These ideas are based on the study of Egyptian and Sudanese 

 brains. 



The idea that partial development of the opercula, leaving the 

 insula exposed, is an indication of low brain development, is quite 

 generally accepted. Cherie-Ligniere (1911) quotes Giacomini as 

 saying that the lack of, or slight development of, the anterior 

 rami fissura Sylvii, which is always joined with a rudimentary 

 development of the inferior frontal convolution and defective 

 development of the insula, are signs of microcephaly of high 

 degree. Wilder (1910) speaks of the insula as being exposed in 



369 



