380 
MR. SKEY ON MUSCULAR FIBRE. 
and ear, diaphragm, intercostals, levator and sphincter ani. The muscles of the tym- 
panum incased in bone, composed so largely of tendinous matter, and apparently be- 
yond the reach of voluntary power, must however be classed among the muscles of 
animal life. Yet they are so intermixed with tendon, that had I not rendered myself 
familiar with the structure and appearance of tendinous fibre, which possesses a re- 
mote resemblance to the muscular fibre of organic life, I should have erroneously 
concluded that they belonged to that class. They possess, however, all the charac- 
ters incidental to the fibre of animal life. 
Organic Life. 
The microscopic view of the muscle of organic or involuntary life exhibits a struc- 
ture essentially different from that of the fibre of the external muscles. 
The difference was first made known by Messrs. Hodgkin and Lister, who state 
that “ the minute fibrillee which enter into the composition of the fasciculi of fibres 
of which this tissue is made up, instead of presenting the transverse striae, are per- 
fectly smooth, and appear to be continued to a considerable length, of nearly uniform 
width.” They describe the fibre as nearly straight and parallel, occasionally inter- 
lacing and dividing among themselves. 
In the muscular fibre of organic life there are no distinct and separable fibres, no 
transverse striae, with one exception, and no appearance of the larger tubes. 
This tissue appears to consist of a series of irregularly disposed lines of various 
thickness, taking for the most part a longitudinal direction, and forming a kind of 
untraceable net-work difficult of delineation. Although there exist no single fibres 
connected by cellular tissue with others around it, yet there is no difficulty in obser- 
ving the direction of the muscle ; for the lines take one course, frequently, however, 
bending to one side and uniting with others around : but the aggregate, though far 
from straight, pursue one general longitudinal direction (Plate XVIII. fig. 3.). The cut 
margin of the object exhibits no projecting fibres, which in the process of prepara- 
tion have started out from their connection with others, or which have evaded the 
straight division with the knife ; but the whole edge is smooth and uniform. The 
drawing is taken from the fibre of the small intestine (jejunum). 
The muscle of organic life appears to possess a smaller proportion of cellular tissue 
than that of the voluntary muscles. None is required for the connection of fibres, 
for in reality there are no fibres in the muscle of organic life, which rather consists of 
filaments interwoven with each other to form the general structure, than arranged 
in parallel lines around the cylinder of each separate fibre, as observed in the mus- 
cular fibre of animal life. 
I could imagine it might be artificially imitated by subjecting a thin layer of these 
latter fibres to a degree of pressure which would destroy the integrity of each fibre, 
and yet preserve the general direction of its filaments. It may be readily distin- 
guished from tendinous fibre, in which the filaments are uniform in size, pursuing 
