114 THOMPSON YATES LABORATORIES REPORT 
surface of the limb, the point of the elbow to the posterior (post-axial) surface of the limb. The 
dorsal line of the limb, along arm and thigh, lie dorsally in the adult Cat and Monkey, and have 
not become displaced to any notable extent either backwards or forwards ; the ventral lines in 
both limbs similarly lie ventral in the adult. 
A torsion of the fore-limb about its own axis is traced by anatomists as having brought the 
distal end of the pre -axial border of that limb, during the pronate position of the fore-limb, into a 
position facing inwards. This view is borne out by the observations in my work. But the 
nerve-analysis in the Monkey indicates a slight torsion in the more proximal part of both limbs, 
for the distal end of the mid-dorsal line of the fore-limb is turned a little backwards as well as 
dorsally when, in a fore-limb capable like the Monkey's of supination at the wrist and elbow, the 
pollex is placed so as to correct the pronating torsion of the limb ; and correspondingly, the mid- 
ventral line passes on the flexor side of the inner condyle, that is, looks a little forwards as well as 
ventral. In the hind-limb the proximal part of the limb also exhibits a little torsion, and in the 
opposite direction to that evidenced in the fore-limb. The distal end of the mid-ventral line is 
set a little backward, that of the mid-dorsal line a little forwards. But in both the limbs the 
amount of torsion thus indicated is quite small, and the indication is of slight twisting, not of any 
rotation of the limb as a whole. The torsion accounts for the tongue-shaped extension from the 
posterior border of the successive spinal skin-fields in the brachial segments, shifting its position 
from — as followed along the limb — the point of the shoulder and the deltoid eminence to flexor 
aspect of the forearm, although assuredly the radial part of that. Conversely, in the lower limb 
the tongue from the hinder edge of the spinal skin-field in the upper crural segments occupies the 
middle of the groin, and in lower segments gradually comes to lie over the subcutaneous surface 
of the tibia, and finally includes the hallux. But this torsion altogether is very slight. 
The mode of distribution of the motor roots to the skeletal muscles (see accompanying 
' Conspectus ') of the limb indicates that the limb is composed of a number of rays placed at 
right angles to the long axis of the body, and parallel with the long axis of the limb. The most 
posterior of these muscular rays are the longest ones, and the most anterior the shortest ones of 
the limb series. The prominence of the limb from the body is of such a form that the anterior 
edge of the prominence is thrust out less abruptly from the side of the trunk than is the posterior. 
Into the anterior edge enter a number of rays ; taking six to be the number of muscular rays in 
the fore-limb of Macacus^ into the segmental composition of its anterior edge there enter four out 
of the six. 
If by a ray be meant a band of muscular tissue extending lengthwise through the 
musculature of the limb, it is not difficult by the degeneration method to trace in the limb the 
rays of the Vth, Vlth, Vllth, Vlllth and IXth spinal segments, and to see that of these the last 
two extend out even to the extreme free end of the limb. The ray of the Xth segment is less 
easily traced throughout its extent continuously. The distal part of it is obvious enough in the 
intrinsic hand muscles ; it is also clear in that part of it stretching between elbow and wrist, tor 
there in Macacus it supplies the flexor muscles. But in Macacus it is unrepresented in the 
musculature of the upper arm, and in the Cat and Dog it is generally absent from the 
