190 Cc. W. M. POYNTER AND J. J. KEEGAN 
two connections with the sulcus praecentralis superior, one with 
the sulcus retrocentralis superior and one with the sulcus retro- 
centralis inferior. In the majority of the hemispheres the 
apparent communications are only shallow grooves. In six 
hemispheres there is a communication with the sulcus sub- 
centralis anterior but in only two of these cases does the fissure 
extend to the Sylvian fissure, which is 8.3 per cent; Retzius 
found the condition in 16 per cent and Cunningham in 19 per 
cent. 
The sulci praecentrales present no unusual features; the most 
common form is a complete separation of the two sulci by a 
superficial gyrus about 5 mm. in width. A union is present 
in 21 per cent. The sulcus praecentralis is united with the sul- 
cus frontalis superior, as in figures 1 and 3, in 79 per cent of cases 
ABBREVIATIONS 
C, Sulcus centralis 
CAL, Sulcus calcarinus 
COL, Sulcus collateralis 
D, Sulcus diagonalis 
FT, Sulcus frontalis inferior 
FM, Sulcus frontalis medius 
FMA, Sulcus fronto-marginalis 
FMED, Sulcus frontalis marginalis 
FS, Sulcus frontalis superior 
FSY, Fissura Sylvii 
IP, Sulcus interparietalis 
ISM, Sulcus interstriatus mesialis 
L, Sulcus lunatus 
LPR, Sulcus limitans precunei 
LSS, Sulcus limitans area 
superior 
OANT, Sulcus occipitalis anterior 
OINF, Sulcus occipitalis inferior 
PARC, Sulcus paracalcarinus 
PI, Sulcus ‘post-sylvius’ 
PL, Sulcus prelunatus 
PO, Fossa parieto-occipitalis 
POL, Sulcus occipitalis, pars polaris 
PR, Suleus precuneus 
PRI, Suleus praecentralis inferior 
striata 
PRS, Sulcus praecentralis superior 
R, Sulcus radiatus 
RA, Fissura Sylvii, ramus asc. ant. 
RCI, Sulcus retrocentralis inferior 
RCS, Sulcus retrocentralis superior 
RH, Fissura rhinalis 
RO, Sulcus rostralis 
ROC, Suleus paraoccipitalis 
RPD, Fissura Sylvii, ram. post. dese. 
RT, Sulcus rostralis transversus. 
RY, Sulcus praecentralis inferior, ram. 
transv. 
SC, Sulcus cinguli 
SCA, Sulcus subcentralis anterior 
SCP, Sulcus subcentralis posterior 
SP, Sulcus subparietalis 
SRO, Sulcus subrostralis 
TI, Sulcus temporalis inferior 
TM, Sulcus temporalis medius 
TP, Suleus temporo-parietalis 
TR, Sulcus transversus 
TS, Sulcus temporalis superior 
TT, Sulcus temporalis transversus 
TTI, Sulcus temporalis transversus 
inferior 
