MUSCULAR ACTION (VOLUNTARY AND INVOLUNTARY) 329 



It cannot be a vital act which closes, and a mechanical one which opens the heart on the one hand ; and a vital 

 act which opens, and a mechanical one which closes the chest on the other hand. 



A theory which involves such a glaring contradiction, and which rehes upon irritability, artificial stimulation, 

 and elasticity as its chief supports cannot be of much account. 



The grand fact remains, that muscles in their normal condition move, and move to definite ends, as apart from 

 irritability, and as apart from external stimulation. The blood does not irritate and excite the heart to action, 

 and the air does not irritate and excite the chest to action. The heart is specially formed to receive, contain, and 

 force on the blood at regular intervals by rhythmic movements, and the chest and lungs perform a like function for 

 the air. 



The movements of the heart and chest, as already explained, are inherent and fundamental, and they go on 

 so long as life lasts, as apart from irritabihty and artificial stimulation. 



The movements of the heart of the chick, as stated, are not dependent on the presence of either blood, muscles, 

 or nerves. When nerves and ganglia are present they perform the role rather of regulating than propelling structures. 

 Similar remarks are, within limits, to be made of the respiratory or chest movements. 



The heart and chest are framed on the same general lines, and their movements are fundamentally the same. 

 They even perform a common work, namely, the transmission and aeration of the blood which feeds the tissues. 

 The right ventricle forces the blood into the lungs, and the chest and lungs force air into the blood — the left ventricle 

 propelUng the aerated blood through the system generally. The presence of bones is not necessary to muscular 

 action ; the heart acts perfectly in their absence. In the chest, the clavicles, scapulae, ribs, cartilages, sternum, &c., 

 supply a scafiolding and protection to the lungs and heart. The chest and heart furnish typical examples of centri- 

 fugal and centripetal rhythmic movements. The opening and closing movements of the chest and heart are 

 mainly, if not wholly, muscular. The chest supplies an outer pulsating chamber within which the heart can pulsate 

 safely : as in " Hamlet," there is a play within a play. 



Much importance in modern times has been attached to the combination of bones and muscles, and the origin 

 and insertions of the latter have been described with scrupulous exactitude. As stated above, bones are not neces- 

 sary to co-ordinated and exact muscular action. When they are present, they are, as a rule, the servants and 

 satelhtes of the muscular system. They are in no instance prime movers. Their main function is one of support ; 

 their secondary function is one of leverage. 



The prevailing theory of muscular action fails in another and most important respect. It requires, as has 

 been indicated, for its realisation that the flexor muscles, when they shorten or contract, shall forcibly drag out, 

 elongate, or dilate the corresponding extensor muscles ; the extensor muscles, when they shorten or contract, forcibly 

 dragging out, elongating, or dilating the corresponding flexor muscles. Here again there is inconsistency. Accord- 

 ing to the generally accepted theory, the flexor and extensor muscles, the pronators and supinators, the abductors 

 and adductors, &c., are made to antagonise, oppose, and contend with each other. 



The fact that the flexors, pronators, and abductor muscles are arranged on one side of the bones to be moved, 

 while the extensors, supinators, and adductor muscles are arranged on the opposite side, does not convert these 

 muscles into antagonists ; in reaUty, they form muscular cycles within which the bones may be said to vibrate. 

 Muscles are, for the wisest of purposes, disposed in groups, and the groups move simultaneously and in sympathy. 

 The groups are co-ordinated ; they are in no way opposed or antagonistic. This is necessary at once for sym- 

 metry, harmony, and economy. Moreover, there are muscles which have no antagonists in the sense required 

 by the theory. The diaphragm is an example in point. The diaphragm, which may be compared to half a heart, 

 half a stomach, or half a bladder, elongates or dilates and bulge? upwards during expiration, and shortens, con- 

 tracts, and flattens in a downward direction during inspiration. The dilating upward and the contracting down- 

 ward movements are equally vital in their nature. The one movement cannot by any possibility produce the 

 other movement. Precisely the same thing occurs in the opening and closing of the several portions of the o3sophagus, 

 of the several parts of the stomach and bladder, and of the different compartments of the mammahan heart. The 

 two auricles of the heart close when the two ventricles open ; the ventricles closing when the auricles open. This 

 follows, because the auricles are so thin that they lack the power to force blood into the firmly contracted and, for 

 the time being, solid ventricles. In the heart, as in the diaphragm, there is no antagonism whatever. There is, 

 further, no antagonism in the movements of any of the hollow viscera. The stomach, bladder, rectum, uterus, and 

 their sphincters all open and close by spontaneous, rhythmic, vital movements at stated intervals, as apart from 



antagonism. 



Antagonism impUes a ruinous waste of power ; it, moreover, ignores the object and aim of all muscular action. 

 Nature does not strive against herself. She conserves her energies, and when she puts them forth she does so on 

 the most advantageous mechanical principles. The object of muscular action, m every case, is to perform work ; 



VOL. I, '^ 



