SECT. 111.] CONTRACTION OF THE MUSCLES. 413 



SECTION III. BY THIS DERIVATION OF THE FLUIDS TO THE 



STIMULATED PART, THE MUSCLES ARE MADE TO CONTRACT, 

 AND MANY OTHER PHENOMENA PRODUCED. 



The fasciculi of the muscles are made up of fibres and 

 carneous filaments, and bound together by sheaths, and are so 

 traversed by blood-vessels, that these are everywhere inter- 

 mingled with the fibres and filaments, and decussate with them 

 more or less transversely; and since the fibres and carneous 

 filaments are closely compressed together by their sheaths, the 

 least congestion and distension of the vessels distributed amongst 

 them cannot take place without the filaments and the fibres 

 which they constitute being thrown into many serpentine in- 

 flexions, and thus their length be diminished. Since, therefore, 

 irritation of the nerves causes congestion of humours in the 

 vessels, it is easy to infer that in this same manner nerves, when 

 irritated, excite the muscles to which they are distributed to con- 

 traction, that is to say, by the greater accumulation of the 

 humour alone, caused in the vessels of the contracting muscle. 

 When the cause, originating in the nerves, which attracts fluids 

 more freely to the muscle, ceases to act, the distended vessels 

 and deflected fibres react by their elasticity on the accumulated 

 fluids, and propel them into the larger blood-vessels not en- 

 tangled amongst fibrils and muscular filaments ; this process is 

 facilitated by the raising of the weight, which resists the con- 

 traction of the muscle that raises it, by the action of the over- 

 stretched muscles antagonistic to it ; and thus the contracted 

 muscle is again relaxed. It is now four years since I sub- 

 mitted this theory of muscular action to the criticism of the 

 learned public, in my Tract, ^De Carne Musculari.^ It is 

 founded on the intimate anatomy of the muscular tissues, is 

 well adapted to the phenomena, and I am not aware that any 

 one has opposed the theory, or advanced any doubts regarding 

 it ; nor in meditating upon it myself have I been able to dis- 

 cover any arguments against it, except that irritability exists 

 more extensively than muscular structure. But it appears 

 to me that this argument, when rightly considered, is not 

 an objection to my theoiy ; for if we observe that polypes 

 and other zoophytes are irritable, in whose structure the 



