MR. SKEY ON MUSCULAR FIBRE. 
383 
Yet there exist some important distinctions, which require considerably more exten- 
sive observation than I have hitherto been able to make ; and I am anxious not to 
commit myself by the expression of an opinion hastily formed as to its composition, 
on which my limited inquiries have hitherto fallen far short of the difficulties of the 
subject. 
It is difficult to explain the experiments of Sir E. Home as regards the muscular 
texture of the stomach which he employed, and which is of the pure structure of or- 
ganic life. I have examined each part, and I have been unable to obtain the least 
trace of animal fibre. The ultimate muscular filaments may be seen in the texture 
of organic, but with by no means the distinctness of animal life, in consequence of 
its reticulated structure which renders them difficult of separation from the bulk of 
the fibre. 
The muscle of organic life pervades the greater part of the oesophagus, the stomach 
including that of the ruminants and the alimentary canal, the trachea and bronchial 
tubes, the uterus , the urinary bladder, the arterial system, and possibly the iris. 
The diameter of all muscular fibres holds a relation to age, being in the human 
foetus, as well as in the young of all the animals in which I have observed it, about 
one third the diameter of that of mature age (Plate XIX. fig. 3.). 
On comparing the muscular fibre of animal and organic, or voluntary and invo- 
luntary life, it does not appear surprising that there should exist the remarkable va- 
riety of structure which I have described. Although both systems are embraced 
under the general denomination of muscle, and possessing the characteristic property 
of irritability, yet their functions in the economy are so distinct, and the power re- 
quired by each is so unequal, that we might almost have conceived the existence of 
an important difference of structure. 
In the muscle of animal life we find the fibres with their subordinate filaments pur- 
suing a direct course between the attachments of the whole muscle, or deviating 
from it merely for the purpose of a convenient adhesion to its common tendon. 
Hence the advantage obtained by a united and cooperating force, by which the whole 
component fibres of the muscle are called into action at the same time. The fibres 
possess no independent influence, but all cooperate to one obvious end, that of ap- 
proximating the extremities of the muscle, and act with a force which, considering 
the nature of their general adaptation, may well be deemed enormous. 
But the power of the muscle of organic life is limited. We find it spread over ex- 
tensive tubular surfaces of membrane, and contributing to the involuntary functions 
of internal life, by a slow and gradually extending contraction. It has no antagonist 
but the contents of the tube it surrounds, its influence on which extends along the 
surface of the muscle, as the contents descend within the tube. 
By means of its matted structure it serves the purpose of a nearly complete invest- 
ment to the canal it surrounds, while its connecting and reticulated composition 
enables it at once to transfer the contents of the tube within the influence of the 
