Page:WHR Rivers - Studies in Neurology - Vol 1.djvu/20

6 more primitive aspects of thermal sensibility from the higher forms on which depend adaptation and the power of discriminating intermediate degrees of heat and cold.

Not one of the descriptive terms for disordered sensation commonly used in clinical reports is free from this ambiguity. Every loss of sensibility must, therefore, be recorded as a function of the test employed; "light touch" gives place to the results obtained with "tactile" and "pressure" hairs, or some similar means of measurement. For "analgesia" we substitute the readings of the algesimeter ("measured prick") or the algometer ("painful pressure"). We do not speak of "loss of thermal sensibility," but report the patient's capacity to react to the more extreme degrees of heat or of cold, and his power of discriminating intermediate temperatures. Similar rules apply to the recognition of measured movement, the compass test and "spot finding": all such expressions as "topognosis" and "perception of posture and space" must be strenuously avoided. All our observations were recorded in terms of the tests employed; and it was this method alone which enabled us to study the integrative transformations to which afferent impulses are subjected on their way from the peripheral end-organs to the highest receptive centres.

Throughout this work we have been occupied with disorders of function, and more particularly with the study of changes in sensation. This cannot be carried out by experiments on animals, in whom it is not possible to obtain any but the crudest sensory reactions.

On the other hand, in man the lesion is not under our control, and the finest examples of functional dissociation occur in otherwise healthy persons; the extent and nature of the structural changes cannot be determined anatomically. In most of the cases where a complete post-mortem examination could be carried out the patient had died from some diffuse injury or progressive disease and, since loss of function always exceeds anatomical destruction, the microscopical picture is no accurate reflexion of the nature and distribution of the sensory disturbance. Moreover, such patients are unsuited for elaborate psycho -physical examination by the very nature of their malady.

We have been guided, therefore, by the following principles in the selection of our cases. For intensive examination we chose those patients in whom the lesion is either stationary or in process of recovery; they must be willing, intelligent, not addicted to alcohol in excess, or subject to epileptiform seizures. We were also influenced in our choice by the illustrative value of the disturbances in function. For example, in cases of Brown-Séquard paralysis we selected more particularly those patients in whom the spacial aspects of sensation were disturbed in one extremity, whilst the qualitative loss was confined to the opposite limb; this enabled us to study the two forms of