1895.] to the Fascia Dentata and to the Nerves of LancisL 99 



certain aquatic mammals completely destitute of olfactory apparatus, 

 e.g., Hyperoodon (bottle-nosed whale), the stria longitudinalis lateralis 

 is present in its usual form, and enlarges anteriorly intosupra-callosal 

 and geniculate convolutions, which are unusually distinct, although 

 minute. B. In megosmatic animals the fascia dentata is continued 

 far beneath the corpus callosum, and only ceases to accompany the 

 fimbria where this body turns downwards in the anterior pillar of the 

 fornix. C. Coronal sections carried through the back of the corpus 

 ca,llosum of an ox-brain revealed no trace of a recurrent fascia 

 dentata. On these grounds 1 assumed that the fascia dentata is a 

 sub-callosal structure. In this conclusion I was, however, completely 

 mistaken, as investigations in progress at the time when my paper on 

 the hippocampus went to press have clearly proved. 



The fascia dentata is continued on to the dorsal surface of the corpus 

 callosum. 



A series of sections carried through the corpus callosnm with the 

 underlying fimbria and fascia dentata, in the brain of a cat, show that, 

 just as the fornix is turning downwards in its anterior pillar, the 

 fascia dentata is folded on itself, and retraces its course back towards 

 the splenium corporis callosi, almost along the middle line of the 

 brain. In this folding the trough of fascia dentata, into which the 

 pyramidal cells of the margin of the cortex are received, remains 

 open dorsally ; at the fold the margins of the trough are slanted some- 

 what forwards. 



A coronal section taken a short distance behind the fold (fig. A) 

 shows the fascia dentata cut twice. On the. outer side it is large and 

 well-developed ; on the mesial side the recurrent fascia is small and 

 narrow. Between the two parts of this folded ribbon is pushed a 

 rounded tubercle of cortex (callosal convolution of Zuckerkandl), 

 which is continuous with the gyms fornicatus. 



Slightly farther back the trough of fascia dentata is reduced 

 to a curved plate (fig. B). This extends but a little way, for, 

 at about half the distance between the folding of the fascia 

 dentata and the spleninm corporis callosi, the stratum granulosum, 

 which has invested the margin of the cortex from the temporal 

 extremity of the hiatus ventriculi to this point, comes to an end. 

 Near the splenium the layer of pyramidal cells which represents the 

 general cortex is reduced to a fold with a bevelled edge, and no indi- 

 cations of its retaining in its tissue any remnants of the characteristic 

 granule layer of the fascia dentata are to be seen. My sections 

 through the corpus callosum of the ox were not carried sufficiently 

 far forward. 



In a certain number of human brains the continuity of fascia 

 dentata and stria longitudinalis through the medium of an interven- 

 ing band, the fasciola cinerea, may be seen very distinctly. 



