446 



BRUGGE) is found. It also exists in the brains of two genera of Ce- 

 bidae, Lagothrix and Ateles. 



In most of the hemispheres (excepting perhaps those of the genus 

 Papio) in which this sulcus is well developed, a ramus dorsalis is also 

 present (Fig. I and 2, s. i. I. [r. d.]) above the caudal end of the main 

 furrow (s. i. l), so that the lateral intrastriate sulci form the character- 

 istic Y-shape. It is interesting to note that the dorsal ramus of the 

 lateral intrastriate sulcus is formed in a manner in many respects ana- 

 logous to that of the ramus dorsalis of the mesial intrastriate sulcus 

 (Fig. 7, s. i. m. [r. ^.]). It frequently happens in all of the Anthro- 

 poid Apes and especially in Man (sometimes also even in Semnopithe- 

 cus) that accessory intrastriate sulci (sulcus accessorius occ. sup. of my 

 former note) develope both below and above the main intrastriate (s. 

 occ. sup.) sulcus. In the human brain these two accessory sulci often 

 unite around the sulcus intrastriatus lateralis (occ. sup.) to form a 

 U-shaped sulcus parallel to the sulcus lunatus. In my former note 

 (Anat. Anzeiger, Bd. 24, No. 2/3, p. 77) I mistook the U-shaped com- 

 pensatory sulcus for the true s. occ. superior (intrastriatus lateralis). 



The points that I wish to specially emphasise the foregoing 

 account are 1) the existence of a definitely specialised cortical area 

 striata (Gennari) occipitalis, the homology of which we can assume in 

 all the Primates: 2) the presence of a definite sulcus praestriatus in 

 most human brains (as well as in all Prosimiae, Carnivora, Ungulata 

 and many other mammals) : 3) the absence or subsidiary importance of 

 this sulcus praestriatus (vel calcarinus proprius) in all Apes — Hapa- 

 lidae, Cebidae, Cercopithecidae and Simiidae: 4) the definite limbic 

 relation of the margins of the occipital operculum (overhanging the 

 sulcus lunatus) and of the inferior occipital operculum (overhanging 

 the sulcus infrastriatus) to the lateral area striata: 5) the presence in 

 most human brains (and occasionally in those of the Apes) of superior 

 and inferior limiting sulci of the mesial part of the area striata and 

 6) the series of intrastriate sulci which extend along the axis of the 

 area striata, both in its mesial and its lateral parts. 



In the introductory remarks I explained that in the evolution of 

 the Simian brain toward the human condition the area striata becomes 

 progressively pushed l)ack on to the mesial surface. Thus the homo- 

 logue of the region which contains the caudal part of the sulcus occ. 

 superior (intrastriatus lateralis) in an Ape's brain will be situated on 

 the mesial surface of the human brain and will contain a sulcus which 

 most writers would call "calcarine" (and in my earlier works has been 

 labelled retrocalcarine). In other words parts of the so-called "cal- 



