188 C. W. M. POYNTER AND J. J. KEEGAN 
widely separated anterior rami, but in the right hemisphere the 
suleus which corresponds in position with the ramus ascendens 
does not reach the limiting sulcus of the .insula, consequently, 
according to Cunningham (’92), this sulcus is not an anterior 
ramus and cannot be homologous to the fissure of the opposite 
hemisphere occupying relatively the same position. This obvi- 
ous inconsistency upholds the theory of Smith (04) in regard 
to the formation of these rami. Another feature which lessens 
the value of data on these rami is the frequent thin opercular 
extension of the pars triangularis to the Sylvian fissure, giving 
rise to a merely superficial appearance of a separation or bifur- 
cation of these rami. 
There is positive evidence of an exposed insula in only one 
adult brain. The brain is that of a female and the condition is 
present in both hemispheres and is accompanied by an unusual 
simplicity of fissuration and a boldly curved fissura rhinalis. 
In several other hemispheres there is indication of defective 
development of the frontal operculum, but the insula is not 
‘sufficiently exposed to place them in the class with the one just 
mentioned. 
The sulcus centralis presents no unusual features such as noted 
for the Sylvian fissure. The most prominent genu corresponds 
to the ‘superior genu’ of authors and is produced by a large 
rounded buttress of the gyrus centralis anterior. While a slight 
shallowing is noted at this level in a number of cases, there is 
no preference between the right and left hemispheres; comparing 
the male and the female shows a greater frequency of the con- 
dition in the male. The average height of this bridging gyrus 
above the floor of the fissure is 4.5 mm. Contrary to Cunning- 
ham’s observation, the fetal brain of this series showed a very 
superficial bridging gyrus in both hemispheres. 
Another point of disagreement with Cunningham’s (’92) 
description of the sulcus centralis is in regard to the operculation 
of the gyrus postcentralis. He states: 
From the seventh month onwards the growth of the two bounding 
banks of the fissure does not proceed at an equal pace. There appears 
to be a greater growth energy in the posterior central convolution, 
