30 C. W. M. Poynter 



Eberstaller has found that the vertical portion may communi- 

 cate with the fissura Sylvii through the sulcus subcentralis an- 

 terior or the sulcus diagonalis (Eberstaller), Cunningham thinks 

 that when connection exists with the fissura Sylvii, an annectanc 

 gyrus can always be found in the depth of the fissure. Retzius 

 finds confluence through the sulcus subcentralis in 9 per cent., and 

 through the sulcus diagonalis in 38 per cent. Cunningham finds 

 connection through one or the other in 42 per cent., and Giacomini 

 in 6t, per cent. 



The most frequent connection of the sulcus praecentralis in- 

 ferior is with the sulcus frontalis inferior, which, on this account, 

 has been considered as a part of the inferior frontal complex 

 (Jensen). Retzius finds this connection in yy per cent, and 

 Eberstaller in 76 per cent. 



The union of the sulcus praecentralis inferior and superior is 

 not unusual as shown by the figures, Retzius 23 per cent., Cun- 

 ningham 32 per cent., and Eberstaller 24 per cent. The sulcus 

 praecentralis superior was first recognized as an independent 

 integer by Jensen, according to Retzius. Its various connections 

 already spoken of constitute its variations, with the exception of 

 an anastomosis with the sulcus frontalis superior and the sulcus 

 paracentralis medialis (Eberstaller). The fissure may terminate 

 superiorly in one or two branches, and Cunningham has shown 

 that it is made up of two parts which may remain separated, 

 Retzius finds in 38 per cent. Communication with the sulcus 

 frontalis superior is the normal condition. Eberstaller finds it a 

 constant condition, Retzius in 86 per cent., and Duckworth in 

 41.2 per cent., for embryos. Farther study is necessary to 

 determine whether separation is an indication of arrested develop- 

 ment. Cunningham describes an inconstant fissure at the mesial 

 extremity as the sulcus praecentralis marginalis, which Duckworth 

 finds present in 50 per cent, of Australian brains. 



The Sulcus Frontalis Mesialis: This sulcus was described by 

 Benedikt as sulcus ' ^,' and later named by Cunningham, who 

 found it present in 100 per cent, of Caucasians ; Retzius con- 

 sidered that it belonged to the sulcus frontalis superior. Its 

 absence in Simiidae and low percentage (.17) in embryos (Duck- 



374 



