72 PHYSIOLOGY. 



much so with regard to what I am going to add, which must be 

 ascertained as a fact, and more clearly demonstrated, before it 

 admits of a particular application." 



C. As the force of cohesion in the muscular fibres of living 

 animals is much greater than in those of dead ones, it is pro- 

 bable from this, and other considerations, that the cause of 

 muscular contraction is an increase only of that same power 

 which gives the contractility of the simple solids, and of other 

 inanimate elastics. (Haller, Prim. Lin. 407- 408.) 



" I have frequently told you, gentlemen, that I am not to 

 entertain you with hypotheses of my own, nor with the descrip- 

 tion of the hypotheses of others, not frequently at least ; but I 

 must say, that if hypotheses are confined to the closet, or even 

 to the college, they are not without their use ; there is no phi- 

 losopher that has not more or less dealt in them ; and in these 

 parts of our science in which we have not made much progress, 

 we shall not go much farther without them, and we shall be 

 tempted to do so according to the importance of the subject. 

 The consideration of muscular motion, the theory of muscu- 

 lar contraction, is of no little importance ; for if we knew it more 

 exactly it would throw light upon every other part of our system. 

 In XCVIII. and XCIX. accordingly I have given a discus- 

 sion which relates to most of the hypotheses that have been 

 offered, and in rejecting error we never lose our labour ; and 

 in C. I have made an approach it is no more than an ap- 

 proach to one of my own. I have in some measure adopted 

 the view of Dr. Haller, by alleging that the cause of muscular 

 contraction is an c alacrior attractio elementorum fibrae, qua ad 

 seinvicem propius accedunt,' (Haller, Prim. Lin. 407-) 'an 

 increase only of that same power which gives the contractility of 

 the simple solids, and of other inanimate elastics/ Now, if the 

 premises in the first part of that proposition could be very well 

 proved, the conclusion which I have just now repeated would 

 be readily enough admitted. But these premises are not yet 

 established with sufficient clearness. Haller refers to one Li- 

 bertus (?) who wrote de mechanices absentia ; and the principal 

 proof which he adduces is, that muscular fibres, in living bodies, 

 sustain a force which in the dead body would tear them in 



