I^rOEPHOLOGY OF THE BRAIX 1\ THE .MAMMALIA. 387 



marked sulcus on tlie mesial surface, which he calls " splen/al/'s " *, a name which has 

 ])een vevy generally adopted. Ue adds: — "According to Eckerf the fissura parieto- 

 occipitalis J develops in the human brain at ahout the same time as or soon after the 

 fissura Sylvii : I am very much disposed to consider it as the homologue of my fissura 

 splenialis " (p. oOD). In a later memoir he describes the splenial sulcus in TJnguiculate 

 Mammals. He explains the [)eculiarities of the fissura liippocampi and the fissura rhinalis 

 as lines of demarcation between cortical areas which are histologically diS'erent. Both of 

 these fissures develop very early, and after their appearance there is a long pause before 

 any other sulcus presents itself. The first one to do so in the Cat's hemisphere is the 

 sulcus splenialis (in a i'lctus of 10+ i"5 cnr. long). In such a foetus it appears " as a 

 flatteucd arc surrounding the posterior end of the corpus callosum and the upper end of 

 the hippocampal fissure, midway between these structures and the upper and hinder 

 margins of the hemisphere " §. 



From a comparison of these interesting facts with those In-ouglit to light ])y 

 Cunningham and Eetzius, the conclusion is forced upon us that, if any sulcus on the 

 mesial surface of the human hemisphere is to be regarded as the homologue of the 

 '• splenial" sulcus of the Sheep and Cat, it must be, not the mor])hologically unstable and 

 unimportant parieto-occipital sulcus which Krueg suggests, but the true " calcarine 

 sulcus." 



That such an interpretation was not entertained by Krueg is obvious from his 

 quotation of Meynert's happy guess j|, when he called "a short ascending branch of the 

 f. splenialis" in the Bear together with a short accessory furrow under it the "sulcus 

 occipitalis," and the f. splenialis itself the "sulcus calcarinus " ^. On the same page 

 Krueg quotes Benedikt as calling " the f. splenialis in the Bear the fissura occipitalis 

 inferior . . . and the mesial part of the f. medilateralis the fissura calcarina " (p. 6i2)**'. 



If, liowever, we adopt Krueg's idea, we must, iu the light of our fuller knowledge 

 of the developmental history of the human brain, regard the splenial sulcus as partly 

 homologous to the calcarine. 



In Broca's Collected Works (p. 321, fig. 20) a short oblique furrow is represented 

 in the hemisphere of a lloebuck, Avhich obviously corresponds to the sulcus Krueg 

 calls " postsplenialis." Broca calls this sulcus " the analogue of the calcarine 

 fissure," whereas he regards the splenial sulcus as part of the "■ limbic fissure."' He 



* Julius Krueg, " I Cber die Furchung der Urosshirnriiide der riigulateii," Zeitsch. f. wissenscli. Zool. Bd. xxxi. 

 p. 308, November ISTs. 



t A. Eckcr, " Zur I'lutwickl. der Fiirchen und AVindungen dei- Grosshiruhemisph. im Fotua des Mensehen," 

 Arch. f. Anthrojiol. iii. Bd., ISO.j. 



± Ecker is ^vroug in Ibis ; for it is the calcarine, and not the parieto-occii)ital, sulcus which develops first. 



§ Julius Ivrueg, " Ueber die Furehung der (irosshiruriiide der zonoplaceiitiileu Saugetiere," Zeitschr. f. wissensch. 

 Zool. Bd. xxxiii., isso. 



II Meyncrt, ' Archiv f. P33cliiatrie,' Bd. vii., liill. The context shows tlial .Meynert's suggested homologies 

 were little else tliau sheer guesswork. 



•[ Krueg, op. tit. p. 041. 



*■* Benedikt, ' .Vnatomisehe Studicn an VerbrechergeLinien," Wien, 1879, 



