1907.| Locahsation of Function in the Lemur’s Brain. 139 
calary fissure. Below this and in front are the various head and face areas. 
The areas controlling the upper limb are posterior to, and somewhat higher 
than these. 
_ The excitation experiments show that, as in the primates, there exist in the 
Lemur three areas related to lower limb, upper limb, and head region 
respectively, from above downwards, in inverse order therefore to the spinal 
arrangement. Moreover, they substantiate and accord with the ablation 
experiments, which will be described later. 
The large size of the hand and finger area is not remarkable in view of the 
habits of the Lemur. It does not pick up its food with the hands in the 
same way in which a monkey does, but as a rule uses the hands to support 
the morsel which is picked up by the mouth. The hand movements are, 
however, undoubtedly more highly developed than in quadrupeds, and come 
chiefly into play in climbing. There is a well-formed and opposable thumb, 
which must be extremely useful in the arboreal life of the animal. We were 
unable to discover any special thumb area in the cortex. 
In the area marked “ upper limb mainly shoulder,” the movements which 
occur spread to the lower part of the limb and the digits on keeping up the 
usual weak stimulation, or by the use of a somewhat stronger current ; the 
resulting movement is a primary one of progression. The same is true for 
the lower limb, especially in those centres which, in the first instance, control 
movements of its upper segment. This spreading does not occur to any 
noticeable degree in the head, face, eye and ear movements. This, again, is 
explicable on histological examination, for the Betz cells in this region are 
much smaller than in the limb areas, and so do not possess so many con- 
nections with other cells. The difference is so marked that we have 
considered it worth while to contrast, in Plate 4, the two types of motor 
cortex. | 
It will be noticed in Plate 2 (fig. 1) that the head, face, and tongue area 
passes on to the outer side of the sulcus rectus. The extent to which this 
occurs probably varies in different animals, but in those subjected to micro- 
scopic study the Betz cells did not extend beyond the outer lip of the sulcus. 
It is probable that this is a more trustworthy guide than stimulation, 
for in the latter method it is often difficult to entirely eliminate spread of 
current. 
In the large area marked “ Pricking of ear” on the outer side of the 
anterior end of the lateral fissure, and which is also characterised by Betz 
cells of the small type, the shaded area near the Sylvian fissure was in some 
experiments the part, stimulation of which elicited the most marked move- 
ments ; this is quite intelligible because in this part one is approaching the 
