Page:The New International Encyclopædia 1st ed. v. 14.djvu/189

* MUSCLE AND MUSCULAR TISSUE. 153 MUSCLE SENSE. HEART MUSCLE. tissue jicfuliar to the lieart. It resembles tlie sniootli invdluiUary niusile in being composed of nucleated cells. These cells are, however, much larger and broader than the smooth muscle cells, ar<> more or less r<'cianf;ular in vha])e, and send olV lateral branches uhiili join similar branches of neighboring.; cells, with which they are cunncctcd by cement substance. The cell protoplasm shows both longitudinal and transverse stria- lions, but much less marked than in striated voluntary uuiscle. A rross-section of a cell gives some- what the a])pearance of C'ohn- heim's lield, but the fibrilhe show a more or less radial arrangement about the circumference. The nu- cleus is round or slightly oval in shape and is situated near the centre of the cell. Development. JIuscle is developed from the mesoderm or middle layer of the embryo. Smooth nmscle cells are produced by a differentiation of mesodermal cells. Voluntary striated muscle is developed by a still further specialization of these mesoderuuil cells, the cell nuclei prolifer- ating and longitudinal and transverse striations appearing in the protoplasm. In this way the cells become gradually transformed into the fibres of voluntary muscle. Heart muscle has the same derivation, and represents an inter- mediate stage of development between the more primitive smooth muscle cells and the more high- ly specialized striated muscle fibres. MUSCLE-READING. The intuition of a person's thought by physical contact. Every complete mental process tends to 'issue' or 'ex- press itself in movement ; the psychophysical organism is essentially a motor organism. In many cases these expressive or concomitant movements are involuntary, and unknown to their performer. It is often possible, by close attention to them, to get an inkling of the object or direc- tion of the agent's thought. Some persons, in- deed, have a peculiar aptitude for this 'muscle- reading,' or {as it has been wrongly termed) 'mind-reading,' so that they are able, by taking into account all the objective indications pre- sented by the agent, to reproduce in somewhat surprising detail the course of his thought. JIuscle-reading was much in vogue a few years since as a drawing-room game. On the stage, it is cust(miary for the 'mind-reader' to lay the hand of the subject upon his forehead, or to take the sub- ject's hand in his own. By minute observation of the subject's involuntary movements, of his trem- or or flush of excitement, etc., it is possible for the reader to guess, in many instances, the number of a watch, the place and character of a hidden object, etc. : the subject being completely unaware that he is giving any suggestion, and the suggestions themselves being imnoticeable to the audience. With the most successful mind-readers the process of observation has liecome habitual and therefore partly unconscious, so that they are unable to explain their modus operandi, even if they desire to do so. Their extreme fatigue, at the conclusion of a performance, indicates, how- ever, that their attention has been under great strain. This appreciation of unconscious movements and of vasomotor changes in the subject is suffi- cient to explain all the feats of mind-reading that are on record, surprising as some of these may appear. Consult: .lastrow, Fact and Fahic in Psyclioloi/ii ( Xew York. 1000); Preyer, Die Kricliirung drs Clcdanlienlesms ( ISSC) ; and Nine- tccnlh Centitri/. xx. 807; Forum, xi. 192; Popu- lar .SViVfici' Monthly, x. 459, .x.xi. 034. MUSCLE SENSE. A term used, in a wider signilicalion, to mean "the sum total of the sen- sations which inform us of the condition 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 ujion the sensations set up in the voluntary muscles. Goldscheider has, however, conclusively proved that the perception of movement is mediated, not by sense-organs in the muscles, but by the sen- sory nerve-endings of the joints (articular sen- sations). Moreover, the definition proposed by Henri must include (or nuist 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 be no justification for retaining the term 'muscle sense' in the meaning indicated. If we wish to group together the sensations concerned in movement, to emphasize their functional conjunction, we may take Bastian's word 'kinsesthetie' sensations. The kintpsthetic "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 ( joinl^sense 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" (Sanfordj. 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. If the position of the arm be 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. When once known to introspection, it can be reproduced by mechanical stinuilation (heavy pressure) as well as by electric current. There is also a special tendinous sensation, mediated by the tendons which attach the vol- untary muscles to the bones. This is the sen- sation of strain, which appears, e.g., when the arm is held out for a considerable time, when the fist is tightly clenched, etc. It is radically dif- ferent in quality from the dead pressure of the muscles, and the .sharp pressure (seemingly identical with cutaneous pressure) that comes