18G1.] BRAIN OF ATELES PANISCUS. 255 



wards, or from within outwards, the hne of this sulcus presents a 

 strongly marked, but irregular, upward convexity. 



On making successive transverse sections of this cerebrum from be- 

 fore backwards (woodcut, fig. 1 . A, B, C, D), the fissure was seen, in its 

 most posterior part (A), to pass almost horizontally outwards for a short 

 distance, and then to divide into an upward and a downward branch, 

 lu front of A it forms a curve strongly convex upwards, without any 

 terminal bifurcation ; in B it is much longer and less convex ; in C 

 it is but slightly sinuous, and in D it is a little concave upwards and 

 inwards. Combining these views with those given in fig. 2, it is easy 

 to form an estimate of the figure of the surfaces of the upper and 

 under lips of the sulcus ; but what is most important about it is, that, 

 so far as the posterior cornu extends, the closed end of this sulcus 

 corresponds with the hippocampus minor (x), which last is, in truth, 

 nothing but the arch of cerebral substance which, at once, forms the 

 outer boundary of the sulcus and the inner boundary of the cornu. 



From its special relation to the hippocampus minor, or " calcar 

 avis," I shall call this the "calcarine" sulcus; but it extends be- 

 yond the calcar and the posterior cornu, both anteriorly and poste- 

 riorly, particularly in the latter direction. Nevertheless it does, in a 

 definite sense, correspond with the inner wall of the posterior cornu. 

 The calcarine sulcus dies away anteriorly, at the point indicated, and 

 is in no way continuous with that sulcus which has a relation to the 

 hippocampus major similar to that of the calcarine sulcus to the 

 hippocampus minor, and which, for distinction's sake, I will call the 

 ' dentate ' sulcus, on account of its relation to the fascia dentata or 

 corps godronne. This narrow and well-known sulcus lies between 

 the letters m and m, the lower m being placed opposite its termination 

 in the fold formed by the recurved part (crochet de I'hippocampe, 

 Gratiolet) of the so-called 'uncinate' convolution (19). Thus the den- 

 tate sulcus, which corresponds with the hippocampus major, is sepa- 

 rated from the calcarine sulcus, which similarly answers to the hippo- 

 campus minor, by the rounded process of cerebral matter, x, this last 

 being, in fact, the inferior and posterior continuation of the callosal 

 gyrus (circonvolution de I'ourlet of Foville, pli du corps calleux of 

 Gratiolet) . This continuation of the callosal gyrus into the uncinate 

 gyrus is regarded as an anomalous peculiarity of the human brain 

 by M. Gratiolet (I. c. p. 64) ; but, so far as I have examined into the 

 matter, it is similarly continued into the uncinate gyrus in Apes. 



Ending at a point considerably anterior to the calcarine sulcus, 

 sometimes in a bifurcated extremity, there is another deep sulcus, n, n, 

 which runs, at first, roughly parallel with /, I, but is much longer, 

 being continued along the inner and under surface of the temporal 

 lobe nearly to its extremity. Although not so deep as the calcarine 

 sulcus, it is continued upwards and outwards, for a considerable di- 

 stance ; and throughout its whole course, the bottom, or roof, of the 

 sulcus underlies the floors of the descending and posterior cornua. If a 

 vertical section be taken through the eminentia collateralis (E, p. 25 1), 

 it will be found that the arch of cerebral substance, e c, whose con- 

 vex side receives that name, by its concave side bounds the sulcus in 



