THE FISSURA HIPPOCAMPI 161 
Martin (94), on the other hand, uses vordere Bogenfurche 
as synonymous with fissura prima and reports that it appears 
dorsal to the choroid fissure. He thinks also that the hintere 
Bogenfurche, a groove in the medial wall in the midst of the 
posterior hippocampus, does not join the anterior Bogenfurche 
until later in development. If his illustrations are carefully 
studied, it appears that Martin’s vordere Bogenfurche is the an- 
terior limb of the hippocampal fissure and seems to become con- 
tinuous with the hintere Bogenfurche when the tip of the temporal 
pole has grown ventrally and rostrally. This finding, if so inter- 
preted, agrees in all poimts with mine. There can be no doubt 
that Martin’s vordere Bogenfurche and His’ fissura prima are not 
the same. Grdnberg (01), however, found no separation of the 
Bogenfurche into anterior and posterior limbs in the hedgehog. 
This finding of Grénberg agrees in all points with that in man, 
namely, a fissure coextensive with the primordium of the hippo- 
campus upon the medial wall. 
Such workers as Hochstetter, Retzius, Goldstein, and Syming- 
ton report that in the region of the primordium hippocampi 
there is a slight thickening of the wall, but no definite infolding, 
although upon careful examination the medial wall at this point 
is not smooth. In other words, these fundamental findings 
agree with those presented in this paper. Investigators who 
concerned themselves with well-fixed brains of the third and 
fourth month did not find the radial folds of the earlier work, nor 
could they identify the fissura arcuata of His. The confusion 
arose out of failure to distinguish between artefacts of fixation 
and the accentuation of normal findings. There is no doubt 
but that maceration plays havoc with the normal contour of 
the medial wall of the hemisphere before the fibers of the corpus 
callosum have lent their stiffness toward its support. His failed 
to emphasize the histological structure which he found in the 
fissura arcuata as peculiarly distinguishing that fissura from the 
accessory fissure above. 
My special contribution to this particular phase of the inves- 
tigation is the discovery that at a certain stage in development, 
the fissura hippocampi is coextensive with the hippocampal 
