AMERICAN NEGRO BRAIN 201 
superior seems to continue without interruption to the temporal 
pole in an arcuate course and with a markedly operculated infe- 
rior lip. The posterior extremity of the sulcus temporalis superior 
is in many instances situated far posterior in the lobulus parie- 
talis inferior so that an unusually large and prominent area of 
cortex is found between the ramus ascendens and the sulcus 
retrocentralis inferior; this area will be referred to again in the 
summary. A fairly constant communication occurs between 
the suleus temporalis superior and the ramus ascendens of the 
sulcus temporalis medius, sulcus temporo-parietalis of this study, 
it can be seen in figures 1, 3 and 5. 
The sulcus temporalis medius is rarely found as a prominent 
single sulcus but is represented by three to five irregular diagonal ~ 
elements. The anterior sulci are arranged in diagonal series 
extending from antero-superior to postero-inferior and frequently 
communicating across the border of the hemisphere with the 
sulcus temporalis inferior; the most anterior of these is frequently 
joined with the sulcus temporalis polaris. The posterior element 
is much larger and deeper than the preceding and runs in a differ- 
ent direction, for this reason it has been termed the sulcus 
temporo-parietalis. It has a fairly constant communication 
with the sulcus temporalis superior, and with the preoccipital 
element of the sulcus temporalis inferior, occasionally it is joined 
to the sulcus prelunatus or to the occipitalis inferior. In no case 
in this series was there found even a superficial communication 
with the diagonal elements of the sulcus temporalis medius. 
The sulcus temporalis inferior is somewhat irregular in details 
but the series presents a general agreement in the number and 
position of the elements making up the fissural complex. Three 
elements are present; the anterior of these is a longitudinal 
sulcus situated a few millimeters lateral to the anterior extremity 
of the sulcus collateralis and frequently communicating with it. 
The posterior extremity of this element is joined to the second 
element in a small number of instances but a bridging gyrus is 
always present. The second element is situated opposite the 
central part of the sulcus collateralis near the lateral border of 
the hemisphere and frequently communicates with the other 
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