ON MUSCULAR IRRITABILITY, 167 



But it is evident that the muscular and nervous systems progressively 

 acquire force from this shock -point, stopping not at their normal amount, 

 but reaching a marvellously abnormal degree of exaltation, and this under 

 the very conditions 1 have pointed out as leading to nervous and muscular 

 exaltation, viz. the absence of the exhausting principle of volition or nerve 

 in action. 



We see, then, by these experiments that muscles possess no abnormal 

 powers immediately after they are liberated from nerve-influence, as in section 

 of the sciatic, or after they are removed from the influence of the upper part 

 of the cord, but that these are gradualhj acciuired, many hours being con- 

 sumed in reaching the maximum degree. The correct explanation, therefore, 

 of Sequard's experiment would seem to be, not that muscle contracts more 

 readily in the absence of nervous influence, but that, in the absence of voli- 

 tional or other excitement, both the nervous and muscular systems can accu- 

 mulate their own special forces, and that to an extent that can never become 

 apparent under normal life conditions. Thus, in the experiment, 60 grammes 

 measure the nervo-museular force of the frogs when unmutilated. After the 

 operation the frog B suflers more from shock, and the sum of its nervo- 

 muscular force is represented in consequence by just half that of the other, 

 or one-sixth of its normal force ; A possesses after the operation one-third of 

 its normal force. The nervoiis system gradually recovers from the influence 

 of shock, but is no longer stimulated by volition, and therefore no longer 

 controls the muscles in the usual way ; consequently they remain flaccid or 

 paralyzed, and this gives them an opportunity of accumulating force, which 

 they gradually do till they acquire nearly three times their normal amount. 

 The exact proportions in which this acciimulated force is divided between the 

 nervous and muscular systems is a delicate subject for future consideration. 



The fact is here broadly stated, that the psychical principle of volition do- 

 minates and exhausts both the nervous and muscular systems, and that in the 

 absence of this influence they acquire exalted powers*. 



I propose now to turn for a short time to a consideration of the part which 

 the blood plays in connexion with muscular contraction. The following is 

 the proposition which I shall endeavour to maintain : — 



That the blood or nutritional plasma derived therefrom not only furnishes 

 the materials by which muscular contractility is maintained, but is likewise 

 the determining cause of that polar arrangement of the muscular molecules 

 which maintaius or restores the elongated or relaxed state. 



* In June 1866, Professor Frankland read a paper to the Eoyal Institution of Great 

 Britain " On the Source of Muscular Force," which contains the following passage : — 

 " The combustible food and osvgen coexist in the blood which courses through the muscle ; 

 hut when the muscle is at rest there is no chemical action between them. A command is sent 

 from the brain to the muscle, the nervous agent determines oxidation. The potential 

 energy becomes active energy, one portion assuming the form of motion, another appear- 

 ing as heat. Here is the source of animal heat, here the origin of muscular foioer. Like 

 the piston and cylinder of a steam-engine, the muscle itself is only a machine for the 

 transformation of heat into motion." The reader will at once perceive that tliis idea of 

 muscular force being generated only during nervou,s action is quite incompatible with tlie 

 experiments and views of the author of this paper. There can be no doubt that chemical 

 action is constantly taking place between certain elements of muscle and blood, and thctt 

 force is being continuously stored, nervous action being concerned in its consumption, and 

 discharge ratlier than its formation. As to heat, it is certainly generated in other portions 

 of the body besides the muscidar structures ; and if nervous action is necessary to oxidation, 

 how is this heat produced ? 



The piston and cylinder are a means of regidating mere repellent force ; but muscle is a. 

 mechanism having the power to convert some fluid, which is either electricity or a close 

 correlate, into a source of botli repellent and attractive power ; for it is only by assuming 

 two such forces that the phenomena of elongation and contraction can be explained. 



