114 On tnuscidar Motion, 



posed ot many substances, in addition to tliose which arc 

 purely muscular. In this gross state they constitute a flexi- 

 ble, compressible solid, whose texture is generally fibrous, 

 the fibres being conipacied into fcciculi, or bundles, of va- 

 rious thickne.-is. These fibres arc clastic during the con- 

 tracted state of muscles after death, being capable of exten- 

 sion to more than one-fifth of their length, and of return- 

 ing again to their former state of contraction. 



This elasticity, however, ap|)cars to belong to the enve- 

 loping reticular or cellular membrane, and it may be safely 

 assumed that the intrinsic matter of muscle is not elastic. 



The attraction of cohesion, in the parts of muscle, is 

 strongest in the direction of the fibres, it being double that 

 of the contrary, or transverse, direction. 



When muscles are capable of reiterated contractions and 

 relaxations, they are said to be alive, or to possess irritabi- 

 litv. This quality fits the organ for its functions. Irrita- 

 bility will be considered, throughout the present lecture, as 

 a quality only. 



When muscles have ceased to be irritable, their cohesive 

 attraction in the direction of their fibres is diminished, but 

 it remains unaltered in the transverse direction. 



The hinder limbs of a frog attached to the pelvis being 

 'Stripped of the skin, one of them was immersed in water, 

 at 113° of Fahrenheit, during two minutes ; when it ceased 

 to be irritable. The thigh bones were broken in the mid- 

 dle, without injuring the muscles, and a scale affixed to the 

 ancle of each limb : a tape passed between the thighs wa? 

 employed to suspend the apparatus. Weights were gra- 

 dually introduced into each scale, until, with five pounds 

 avoirdupois, the dead thigh was ruptured across the fleshy 

 bellies of its muscles. 



The irritable thigh sustained six pounds weight avoirdu- 

 pois, and was ruptured in the same manner. This experi- 

 ment was repeated on other frogs, where one limb had been 

 killed by a watery solution of opium, and on another where' 

 essential oil of cherry laurel* was emploved : in each expe-. 

 riment the irritable limb sustained a weight one-sixth hea- 

 vier than the deatl limb. 



It may be remarked, in confirmation of these experi- 

 ments, that wiien muscles act more powerfully or'more ra- 

 pidly than is equal to the strength of the sustaining parts, 

 they do not usually rupture their fleshy fibres, but break 

 their tendons, or even an intervening bone, as in the in- 



* Dial il'.ed oil from tlie leaves of tlie prmius lauro'ccams. 



Stances 



