156 
DR, C. E. BEEYOR AND PROFESSOR V. HORSLEY ON A 
4. Value as a Determinant of Localisation of Function.— We do not intend here to 
dwell on this point, because its full importance will be seen in the subsequent descrip¬ 
tion of our experimental results obtained by stimulation, but we will anticipate so far 
as to say that this sulcus enjoys the distinction of separating the seat of the primary 
representation of the upper limb from that of the lower, a distinction which, it need 
hardly be added, is of the first importance. 
Thus we have been led to designate this sulcus, x, by the more definite term of 
superior frontal sulcus, and we trust that the above evidence will be accepted as 
tending to establish this position. 
The Intra-parietal Sulcus .— There is one variation in the form of this sulcus which 
we will notice, not merely because, so far as we know, it has not been described before, 
but also because it alters slightly the localisation of certain movements of the digits. 
This variation simply consists in a bending horizontally forwards of the lower end of 
the sulcus towards the fissure of Rolando, from which, in extreme cases, it is some¬ 
times separated by only 3 mm. of surface of grey matter. This is particularly marked 
in the pig-tailed Monkey ( Macacus nemestrums). We shall refer to this point 
further. 
Ascending Parietal Convolution. —We would draw attention to the fact that the 
upper end of this convolution—in other words, that part which represents in Man the 
parietal lobule—is invariably subdivided vertically by a subordinate sulcus, which is 
situated at the junction of the anterior and middle thirds of the convolution and runs 
down parallel to the fissure of Rolando. The lower end of this subordinate sulcus 
extends most frequently to the level of x, the upper end always being separated from 
the margin of the hemisphere by a few millimetres of cortex. 
With the foregoing observations we conclude the anatomical description of the part 
under consideration. 
Previous Researches in the same Direction. 
We will now describe the results obtained by Professor Ferrier on stimulating 
the same region, quoting verbatim from his £ Functions of the Brain,’ 1st edition, 1876. 
From the account there given we have drawn up the following Table, showing the 
relation between his nomenclature of centres stimulated and ours, and in the third 
column the results he obtained. 
We find, however, that the area of cortex in which the upper limb is represented 
extends a little further towards the fissure of Sylvius than he has indicated; it is 
difficult also to make out the exact position of our centres 2 and 2' in relation to his, 
but perhaps we may include them in his centre 6. 
With these trifling differences, it will be seen that the broad facts in our account 
are practically identical with his, all minuteness of detail contained in the following 
pages being of course superadded by us. 
