52 The Rice Institute Pamphlet
bounded by the lateral fissure. The temporal lobe is marked
off by the lateral fissure and extends laterally and ventrally.
The occipital lobe is located at the rear of the cerebrum, but
is not separated by any major fissures. (For the purposes of
this paper it will be appropriate to consider cortical areas
in animals as comparable to those described here for the
human cortex.)
The work that had been done by 1900 placed the cortical
representation or projection of somatic sensory processes in
the parietal lobes in a narrow region adjacent to the central
sulcus. The motor processes were localized in the frontal
lobes just anterior to the central sulcus. Along each of these
narrow strips it was possible to identify topographical repre-
sentations of the body for both sensory and motor processes
beginning at the top of the hemisphere and extending down
the side in the following order: foot, leg, trunk, neck, arm,
hand, face, and throat (Ferrier, 1886, Ch. VIII; Sherrington,
1906, Lecture VIII). More recent work using more refined
techniques has substantiated these early finding (cf. Penfield
& Rasmussen, 1950, pp. 213-216), but has made it necessary
to change the interpretation of their significance. In order to
be able to clarify this change in interpretation it will prove
helpful to describe in some detail the procedures involved in
systematic electrical stimulations of the human cortex during
operations on the brain.
Penfield and his colleagues (Penfield & Rasmussen, 1950;
PenfieId & Jasper, 1954) have performed more than four hun-
dred operations on the human brain for the removal of
tumors or other sources of epileptic disturbance. In order to
insure the excision of all the diseased tissue it is necessary to
identify precisely the limits of the pathological area. At the
same time precautions must be taken to minimize interfer-