Interaction between ipsilateral spinal reflexes acting on the flexor muscles of the hind-limb

Abstract

The structural scheme of the nervous system involves overlap in the terminal distribution of the afferent arcs converging on the final motor units. A physiological consequence attaching to this extensive overlap, so far as concerns one of its two main categories, forms the subject of the present enquiry. The convergent junctions which, subserving the ‘principle of convergence’ (25), result from the overlap, present for functional examination a twofold set of cases. Composing one main class are those cases in which the afferent arcs converging upon the common unit or path tend to act on it to like effect, i. e ., in which there flexes are 'allied’ (27). The other class is that where the convergent arcs meeting at the common unit are such as act there to opposed effect, i. e ., are 'antagonistic’ (27). This latter, namely the class of antagonistic reflexes, in which excitation reacts against inhibition and vice versa , has since its formulation been a frequent subject of experimental enquiry and possesses a not inconsiderable literature. On the contrary the case of interaction of 'allied' reflexes has attracted little experimental enquiry and received relatively little attention. In 1909 observations by Camis (8) were devoted to it and revealed features of interest inviting further study. These observations of Camis (8) were dealt with in our recent paper (9), which, while confirming and somewhat extending them, indicated that the problem of the interaction of allied reflexes must be met in the body by some co-ordinative solution playing a great role in the reflex taxis of the limb. The present observations had in view to observe the modus operandi obtaining between a typical pair of allied reflexes embouching upon a final path, for which both are excitatory.