MUSCLE SENSE. A term used, in a wider signification, to mean "the sum total of the sen sations which inform us of the c•undition of our motor organs" (Henri). This usage has its root in the theory that our chief reliance, in per ceptions of the movements of our limbs, is upon the sensations set up in the voluntary. muscles. Ooldscheider has, however, eonclusively proved that the perception of movement is mediated, by sense-organs in the muscles. but by the sen sory nerve-endings of the joints (articular sen sations). More,)ver, the definition proposed by Henri must include (o• must tacitly ignore) visual sensations: for we undoubtedly derive a good part of our knowledge of movement by seeing our limbs move. There seems, then. to he no justification for retaining the term 'nmsele sense' in the meaning indicated. H we wish to group together the sensations concerned in movement, to emphasize their functional conjunction, we may take Bastian's word 'kinaesthetic' sensations. The kinfesthetie "group of senses furnishes us with data for the perception of the positions and motions of our members and of the body as a whole, and plays a leading part in the perception of space. It includes some senses whose existence or efficiency is disputed (innervation sense and muscle sense), and others whose independence has only of late been generally recognized and tendon sense). All are closely united with one another and with pressure and contact, and some are hardly ever dissociated except by dis ease" ( Sanford ) .
The specific sensation of the voluntary muscle, `muscular sensation' in the narrower sense, al though it is of little functional import (except, perhaps. as the chief sense-basis of the feeling of muscular fatigue), is easily isolated by labora tory procedure. H the position of the arm lie kept constant, so that there is no change of articular sensation, the cutaneous sensations ruled out by etherization, and an induction cur rent passed through the body of a muscle, we get a dull, diffuse, vague sensation, which is localized in the substance of the arm. With high
degrees of muscular contraction, the sensation takes on a dragging or grinding character, and presently verges on pain (q.v.). It is unques tionably a specific sense-quality, best described as a dull. dead pressure, and most nearly akin to (though by no means identical with) the pressure sensations obtained by lightly pressing a blunt object upon the cutaneous surface. \Vhen once known to introspection, it can be reproduced by mechanical stimulation (heavy pressure) as well as by electric current.
There is also a special tendinous sensation, mediated by the tendons which attach the vol untary museles to the hones. This is the sen sation of strain, which appears. e.g., when the arm is lurid out for a eonsiderable time, when the fist is tightly clenched. etc. It is radically ferent in quality from the dead pressure of the muscles, and the sharp pressure (seemingly identical with cutaneous pressure) that comes from the articular surfaces. It plays a large part in the perceptions of weight, resistance, etc.. enters into the fatigue-complex of exhaust ing bodily exercise. and occurs in muscular cramp. Its variations do not necessarily run parallel to the variations of the muscular sen sation. for very different degrees of muscular contraction are, obviously, compatible with one and the same :1111.1Illei of pull upon the tendons. Consult: C:o)dsc•heliler, .1/)/minnu n gen, vol. ii. (Leipzig, Isles) : Bastian. The Brain as an Organ of Mind (London. ISS3I Henri, in .move• p..syeholoqiyae•, vol. v. ( Pa ris. 1800) ; Titehcmee•, ExperimcnIal Psychology, vol. i. (New York, 1901).