402 MUSCULAR MOTION. 



rial blood; others to a union of the particles of the muscular fibre with 

 the nervous fluid; and others, to the disengagement of an elastic gas, 

 primitively contained in the blood, and separated from it by the nerv- 

 ous spirits. It would, however, be unprofitable, as well as uninterest- 

 ing, to repeat the different absurdities of this period so prolific in 

 physical obscurities. Medicine has generally kept pace with physics, 

 and where the latter science has been dark and enigmatical, the former 

 has been so likewise. In physiology, this is especially apparent; most 

 of the natural philosophers of eminence having applied their doctrines 

 in physics to the explanation of the different functions of the human 

 frame. Newton, Leibnitz, and Des Cartes, were all speculative physi- 

 ologists. The discovery of electricity gave occasion to its application 

 to the topic in question; and it was imagined, that the fibres of the 

 muscle might be disposed in such a manner as to form a kind of battery, 

 capable of producing contraction by its explosions; and after the dis- 

 covery of galvanic electricity, Valli 1 attempted to explain muscular 

 contraction, by supposing that the muscles have an arrangement simi- 

 lar to that of the galvanic pile. Haller 2 endeavoured to resolve the 

 problem by his celebrated doctrine of irritability, which will engage 

 attention hereafter. He conceived, that the muscles possess, what he 

 calls, a vis insita; and that their contraction is owing to the action of 

 this force, excited by a stimulus, which stimulus is the nervous influx 

 directed by volition. This, although a true doctrine we think, sheds no 

 new light on the mysterious process. It is, in fact, cutting the Gor- 

 dian knot. We should still have to explain the precise mode of action 

 of the vis insita: 3 but that it is not in any way derived from the nerv- 

 ous system will be shown when treating of LIFE. 



The hypothesis of Prochaska 4 is entirely futile. He gratuitously 

 presumes, that minute ramifications of arteries are every where con- 

 nected with the ultimate muscular filaments, twining around them, and 

 crossing them in all directions. When these vessels are rendered 

 turgid by an influx of blood, by passing among the filaments, they 

 must, he conceives, bend the latter into a serpentine shape, and thus 

 diminish their length, and that of the muscle likewise. Sir Gilbert 

 Blane, 5 again, throws out a conjecture deduced from experiments, in 

 which he found that the actual bulk of a muscle is not changed during 

 contraction, but that it gains in thickness exactly what it loses in 

 length ; that this may be owing to the muscle being composed of 

 particles of an oblong shape ; and that when the muscle is contracted, 

 the long diameter of the particle is removed from a perpendicular to a 

 transverse direction. But the same objection applies to this as to other 

 hypotheses on the subject; that it is entirely gratuitous, resting on 

 no histological observation whatever. 



Two views have been, perhaps, the most prevalent ; one which con- 

 siders muscular contraction to be a kind of combustion ; another that it 



1 Experiments in Animal Electricity, Lond., 1793. 



2 Element. Physiol., xi. 214; and Oper. Minor., torn. i. 



M. Hall, art. Irritability, Cyclop, of Anat. and Physiol., July, 1840. 

 * De Came Musculari, ii., Vienn., 1778. 

 6 Op. citat. 



