16 Proceedings of the Royal Physical Society. 
superficially; a frequent seat for such a connecting con- 
volution is at the angle of its ascending and _ horizontal 
portions, excellent representations of which may be seen in 
the brains of the Bushwoman, figured by Professors Gratiolet 
and Marshall.” Sernoff and Cunningham have investigated 
the relation between the various elements composing the 
intra-parietal sulcus. It is interesting to note that, while 
in the majority of the apes these elements unite to form a 
fissure, such as Turner described, Cunningham found that 
in sixty-three adult Irish hemispheres it only occurred in 
19:1 per cent. of the cases, while Sernoff found it even less 
frequently in adult Russian brains. Cunningham found 
the most common condition to be that in which the two 
portions of the vertical sulcus and the horizontal one were 
all united. 
We do not as yet know sufficient regarding the develop- 
ment of the fissures in the brain of the apes to express a 
definite opinion, but it is very probable that various fissures, 
which in the human brain are developed from two or more 
separate elements which subsequently fuse, are formed in 
the apes from a single fissure. Thus it is now well known 
that the fissure of Rolando is developed in the human 
subject from two elements, a superior and an inferior. In 
the process of development they exhibit a very decided 
tendency to join, but occasionally we meet with a fissure of 
tolando in the adult, composed of an upper and a lower part 
quite distinct from one another; and in the majority of 
human brains the fissure of Rolando will be found to be 
shallower at the point of union of the two original elements 
than above and below. The anthropoid apes will doubtless 
show a condition intermediate in this respect between man 
and such apes as the baboon and macaque. 
The Island of Reil and its Opercula—Many interesting 
points connected with the relative development of the brain 
in man and the apes are revealed by a study of the island of 
Reil and the portions of the cerebral cortex adjacent to it. 
It is well known that in the human brain, before the middle 
of foetal life, the island of Reil lies fully exposed on the 
outer aspect of the undisturbed brain, while in the adult it 
