EXAMINATION OF SOME SPINAL NERVES 153 
But not only are certain of the movements about a single joint opposed to each other, 
certain movements at one joint are opposed to certain movements at neighbouring joints. Thus 
the extensors of the knee may be called antergetic not only to the flexors of the knee, but also 
to the flexors of the hip. In such cases the rule above given still holds. The groups of motor 
neurons selected by the reflex action as it irradiates over spinal segments lying apart in the limb 
series are still those of synergetic muscles. For instance, while the reflex movement evoked by 
excitation of the IVth post-thoracic afferent root, or that responsive to the long saphenous nerve, 
usually primarily contracts the flexors of the hip, it involves next, not the antergetic muscles in the 
nearest spinal segments [c.g.^ vasti and crureus), but neglects these and embouclies into the 
synergetic of more distant segments, e.g., the hamstring muscles. In this way, the reflex action, hy 
its spread, develops a combined movement, synthesizes a harmony.* Broadly put, there is elicitable as a 
pure spinal reflex from the lumbo-sacral region, but one movement of the limb as a whole. This 
movement is a combined movement of general advance and flexion of the limb. It is combined 
of flexions of hip, knee, ankle (dorso-flexion), and digits. These components of the combined 
movement appear, in accordance with the rule of segmental proximity, to be each rather more 
readily elicitable via afferent roots of the segmental locality of their own motor neurons, than via 
roots belonging elsewhere. Nevertheless each, when the excitation is pushed, tends to have 
associated with it more or less of the rest of the general movement of flexion. It is hardly too 
much to say that there is in this limb-region of the cord of, for instance, the Dog, from the point 
of approach of the local afferent channels, but one motor centre, and this the one which produces 
general flexion of the limb. Into it at one point or another lead all and each of the afferent 
channels which provoke movement of the limb at all ; and the outcome is therefore, broadly 
stated, monotonously flexion. Similarly, with the fore-limb the combined movement of flexion at 
elbow, extension at wrist, and flexion [i.e., retraction) at shoulder, is the movement elicitable from 
the limb as its local homonymous spinal reflex action. There is, however, it is true, emphasis on 
or predominance of this or that detail, according as this or that particular nerve-root or nerve-trunk 
affords the particular channel of approach. The arrangement of the intra-spinal resistance is such 
as to make certain functional groups of the motor neurons especially easy of access to, broadly 
speaking, all the afferent channels of the limb. Inasmuch as the motor groups thus found to be 
especially easy of access are such as, when synchronously active, give one harmonious movement 
of the whole limb — e.g., drawing it upward and forward by co-operative flexion at the various 
joints — these groups can be considered to constitute one large functionally-connected nucleus, 
which itself may constitute an entity in the co-ordination of the limb in the movements of the 
body taken as a whole.t It is conceivable that such a nucleus is dealt with as a whole, especially 
when the long cerebro-spinal arcs — ruptured in my experiments — remain intact. 
* It must be remembered, however, that the extensors at some joints are synergetic, not antergetic, to the flexors at other 
points ; this has been especially shown by H. E. Hering in an article published since this communication was sent to the Society. 
Hering calls such muscles pseudo-antagonistic to each other. An example of such action, especially studied by him, is the 
pseudo-antagonism of the extensors of the hand with the flexors of the fingers. — lo July, 1897. C. S. S. 
f This prediction was confirmed in two Notes communicated by me to the Society (' Cataleptoid Reflexes in the 
Monkey,' Proceed, of Roy. Soc, Dec, 1896. 'Reciprocal Innervation of Antagonistic Muscles,' Third Note, Dec, 1X96), 
after the present paper had been sent in. — loth July, 1897. C. S. S. 
U 
