THE FISSURA HIPPOCAMPI 77 
morphological significance and was in no way related to the 
hippocampal fissure. In one brain he was able to trace the 
hippocampal formation from the region of the temporal pole to 
that of the developing transverse commissures. He further 
called attention to the fact, formerly supported by comparative 
anatomy alone, that the gray and white formation above the 
corpus callosum in the adult human brain is the remains of a 
hippocampal formation. 
Mall (03) examined some fifty brains in his collection. He 
found that those fixed in alcohol or in weak formalin showed fis- 
sures on the medial wall, while those fixed in strong formalin 
showed no such structures. He concludes ‘‘according to the 
experience of Hochstetter, Retzius and myself, the transitory 
fissures are not found in fresh brains. They are therefore arte- 
facts and of no morphological significance.” 
G. Elliot Smith (03, p. 217) says: ‘‘Two kinds of so-called 
‘transitory fissures’ have been described in the fetal human 
brain. There is the group of irregular puckerings of the neo- 
pallium, which are found in those fetuses of the 3rd and 4th 
months in which putrefaction changes have begun; and there is 
a second group which are found in fetuses of the 5th, 6th and 
7th months. It is quite unnecessary to discuss the first group, 
because their true nature as postmortem wrinklings of the neo- 
pallium has been conclusively demonstrated by Hochstetter, 
and the results of the examination of all known fresh fetuses 
of the third and fourth months amply confirm the results obtained 
by Hochstetter’s researches.” 
The heat of the discussion centered around His. But in no 
instance did he describe the radial folds of Cunningham and the 
earlier workers. His findings may be compared to those of 
Retzius (01), although they share neither the terminology nor 
the interpretation. In the young embryos (His, ’04, fig. 40, 
embryo C. R. 13.6 mm.) he describes the fissura prima, the an- 
terior and posterior arched fissures and the fissura rhinalis; in 
later embryos, he adds the fissura arcuata accessoria and the 
fissura calcarina. The fissura rhinalis and fissura calcarina are 
permanent: and morphologically significant structures. The 
