146 Drs. F. W. Mott and W. D. Halliburton. [Nov. 14, 
correspondence of the results so obtained with those obtained experimentally — 
is well seen by comparing together the figures in the text with Plate 2 
(fig. 7). 
5. There are, however, two types of motor cortex in the Lemur’s brain, 
and these are shown side by side in Plate 4. The large type of Betz cell is 
found in the greater part of the motor cortex, particularly where limb and 
body movements are represented. The smaller type of Betz cell is found in 
the area governing face, tongue, ear, and eye movements, and in this 
excitable region there is a layer of granules; it is therefore probably sensori- 
motor. : 
6. Although the investigation relates in the main to motor representation, 
histological examination of the occipital (and especially calcarine) region 
shows it to possess the structural characters of the visual cortex in other 
animals. That no eye movements could be elicited by faradic stimulation of 
this region is probably due to the difficulty of the experiment, as explained 
in the text. 
The expenses of this research have been in part defrayed from grants made to us by 
: . : £ : 
the Government Grant Committee of the Royal Society, and by the Science Committee 
of the British Medical Association. 
DESCRIPTION OF PLATES. 
PEATE 2, 
Fie. 1.—This is a map of the Lemur’s cerebrum from above. The names of the principal 
sulci, and the position of the subdivisions of the motor area, as ascertained by the stimula- 
tion method, are shown on the right hemisphere. The homologies of the small sulci, 
marked (1) and (2), are discussed in the text. 
Figs. 2--8.—These show a series of drawings made from the central nervous system 
of Lemur 7, in which the upper limb area was removed. The course of degeneration is 
indicated by black lines and dots. 
Fig. 2 is a section of the injured right hemisphere. The position of the lesion is indi- 
cated by a dotted line, and degenerated fibres are seen passing in three directions, namely, 
by the corpus callosum to the opposite side, by association tracts to adjacent convolutions, 
and by the internal capsule to the cerebral peduncle. 
Figs. 3, 4,5, and 6 are sections at various levels of the pons and bulb. Decussation 
of degenerated fibres begins at a lower level than in the case of Lemur 9 (in which the 
head area was removed, Plate 3, figs. 1—8), and at a higher level than in the case of 
Lemur 8 (Plate 3, figs. 9—16), in which the leg area was removed. 
Fig. 7 is a drawing through the thoracic region of the spinal cord ; a few degenerated 
fibres are still seen in the crossed pyramidal tract, but these have entirely disappeared in 
the lumbar region (fig. 8). 
