on Muscular Motion . 
219 
| broad, was treated in the same way, and its muscular con- 
traction was found to be i of an inch, that from elasticity ± of 
an inch. 
A third portion of membrane of an inch long, and -f broad, 
was ascertained to have contracted f of an inch by its mus- 
cular power, and -f from its elasticity. 
It will scarcely be necessary to mention, that the muscular 
contraction in this membranous structure, is very readily over- 
come, since this must be almost self-evident ; that circum- 
stance, however, must be particularly attended to in making 
similar experiments. 
The internal membrane of the urethra we know to be ca- 
pable of contracting, as spasmodic strictures are formed in that 
canal. This membrane, when dried and examined in the mi- 
croscope, has not the same appearance as the coats of the hy- 
datid ; but the whole is a congeries of vessels forming a net- 
work. We must, therefore, suppose that the action is in these 
very minute vessels. 
From these experiments and observations, membranous 
structures are found to exert an action hitherto denied them ; 
and it is equally evident, that this principle is applied to the 
purposes of the animal oeconomy in a more extensive manner 
than has been generally imagined. 
To explain even the most obvious phenomena of muscu- 
lar motion, must appear from the above observations to be 
attended with difficulty ; how arduous then the task of inves- 
tigating the principle upon which that motion depends ; a 
principle as extensive as life itself, with which it is coeval, and 
indeed the only criterion we have of its existence. 
