LresEM, Fore-Brain of Macacus. 3 
inferior occipital, the par-occipital, the calloso-marginal, and 
the calcarine fissures divide the hemispheres of Macacus into 
frontal, parietal, occipital, and limbic lobes. A brief descrip- 
tion of these fissures is therefore desirable at this juncture. 
The Sylvian fissure is oblique in direction. In man it is 
horizontal, in carnivores almost vertical. It starts at the base 
of the brain, separating the orbital surface of the frontal from 
the temporal lobe. At first it proceeds laterally, then ob- 
liquely upwards and backwards, and finally terminates by join- 
ing the parallel fissure. In one specimen of Macacus nemes- 
trinus under observation, the Sylvian fissure did not join the 
temporo-sphenoidal. Owing to the non-development of the 
orbital surface of the frontal lobe, the sylvian fissure in Macacus 
rhesus has no anterior limb. In Macacus nemestrinus, how- 
ever, there exists a small rudimentary fissure occupying the 
position of the anterior Sylvian limb, but not continuous with 
the Sylvian sulcus. 
The fissure of Rolando is very similar in its course to that 
of man. It runs from just below the great longitudinal fissure 
and curves sharply forwards and downwards. Before its termi- 
nation, just above the mesial portion of the Sylvian fissure, the 
fissure of Rolando curves slightly backwards. 
The par-occipital fissure runs sinuously from the great 
longitudinal fissure almost to the inferior margin of the hemis- 
phere. Externally it is hidden from view by the growth for- 
ward of the occipital lobe. This growth forward of the occi- 
pital lobe results in the formation of a fissure, the ‘‘Affen- 
spalte.’’ This fissure, called by some the external occipital 
sulcus, is peculiar to Quadrumana. Upon drawing aside the 
‘“‘Affenspalte” we find lying in its floor two annectent gyri 
belonging to the par-occipital fissure. The par-occipital fissure 
is joined by the parallel and the intraparietal sulci. 
The inferior occipital fissure extends from the posterior 
margin of the occipital lobe almost to the parallel fissure. It 
is curved forwards and upwards, and passes just below the 
‘‘Affenspalte.”’ 
The calcarine fissure lies upon the mesial aspect of the 
