42 



C. ]V. M. Poxntcr 



occipitalis (Smith). The s:;roiip of fissures which make up this 

 complex show great variation in arrangement and when partially 

 or completely covered hy opercula. as suggested, may be over- 

 looked and thus form the fissura parieto-occipitalis of authors. 

 Smith ( IQ04) has found this group to be made up of the sulcus 

 paracalcarinus, incisura parieto-occipitalis and sulcus limitans 

 praecunei, and says that all may be represented. Zuckerkandl 

 (1908) has made a ver\- extensive study of this fissure complex; 

 he finds that there are nine fissure combinations possible in the 

 human brain, and that there are four elements in the complex, 

 viz, sulcus gyri transitorii, sulcus parietahs superior, sulcus 

 limitans praecunei, and sulcus parieto-occipitalis medialis. Both 

 authors show the absolute untrustworthiness of the ' fissura 

 parieto-occipitalis ' as a landmark and consequently the w^orthless- 

 ness of measurements made from this point. They also show the 

 great variation in size and shape of the cuneus. 



Smith (1904c) boinuls the lobulus parieto-occipitalis in man by 

 the sulcus limitans praecunei and sulcus paracalcarinus. He 

 thinks the latter the older and is also of the opinion that the 

 lobulus is a primitive form of the fissure complex in the human 

 brain. Zuckerkandl shows that the variability of the sulcus 

 parieto-occipitalis makes the boundaries of the lobulus uncertain, 

 and since the same condition of variability obtains for the lower 

 primates, no homology can be established. 



(. hxlinarily the fissura parieto-occipitalis is in communication 

 with the fissura calcarina. Cunningham thinks that, except his 

 type v., there is a deep anncctant to mark the point of separation 

 of one from the other fissure. When this bridging convolution 

 reaches the surface, it is called the gyrus cunei (Cunningham). 

 Its presence is reported by Retzius in 2.5 per cent., by Cunning- 

 ham in 3.9 per cent., by Weinberg in 4 per cent.. Giacomini in 1.8 

 per cent.. Sergi (Herero) 7 per cent.. Ronfigli in a per cent., and 

 Benedikt (criminals) in 6 per cent. 



Fissura Calcarina: Cunningham (181)2) found that this fissure 

 was made up of two jM-incipal segments. Retzius ( 1896) appar- 

 ently did not agree with this tlivision. for he considered it as one 

 fissure. Smith (1904) re-emphasized the division made by Cun- 



386 



