94 THOMPSON YATES LABORATORIES REPORT 
ventral (anterior) roots of which supply the innervation of the muscles in question. Further, the 
Vllth is the chief root of the muscles, both as regards sensory fibres and motor. It is noteworthy 
that the effects of excitation of these afferent nerve-fibres from muscle, both on blood pressure 
and respiration, were not the converse of, but similar in character, to those from internal 
saphenous nerve, though not so extreme. 
The conclusion arrived at by each of the four lines of observation is, therefore, that the 
afferent nerve-fibres distributed in a given muscle arise in the root-ganglia of exactly those spinal 
segments whence emerge the tnotor-fihres for the same muscle. In other words, tlie sensory nerve-cells, 
directly connected with a given skeletal muscle, are in any one individual always of the same seg- 
mental level as the motor nerve-cells connected with the same given muscle. The simplest reflex 
path connected with a muscle may, therefore, be expected to lie exactly in the particular segments 
whence issue the motor-fibres to the muscle. In the 'knee-jerk' we have evidence of a muscu- 
lar reflex arc, traceable usually principally /rum and into vastus media lis and adjacent part of crureus, 
and this affords, as it were, a test case for the above conclusions ; it confirms them perfectly ; it 
exemplifies them by its narrow local extent, and by the segmentally horizontal, correlative position 
of its motor and sensory components. 
