on muscular Motion . 
3 
of their length, and of returning again to their former state of 
contraction. 
This elasticity, however, appears to belong to the enveloping 
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 con- 
trary, or transverse direction. 
When muscles are capable of reiterated contractions and 
relaxations, they are said to be alive, or to possess irritability. 
This quality fits the organ for its functions. Irritability 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 
115 0 of Fahrenheit, during two minutes, when it ceased to 
be irritable. The thigh bones were broken in the middle, 
without injuring the muscles, and a scale affixed to the ancle 
of each limb : a tape passed between the thighs was employed 
to suspend the apparatus. Weights were gradually 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 avoirdupois, 
and was ruptured in the same manner. This experiment 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 employed : in each experiment, the 
* Distilled oil from the leaves of the Primus Lauro-cerasus. 
B 2 
