MR. SKEY ON MUSCULAR FIBRE. 
381 
individually one unvarying line, each filament being parallel to those around it. This 
great regularity in arrangement renders tendinous fibre a microscopic object of 
singular beauty and delicacy, when it has not been subjected to a coarse manipula- 
tion (Plate XVIII. fig. 4. b.). 
To the general description of the muscular fibre of organic life, the heart forms an 
important exception (Plate XVIII. fig. 5.). It appears to possess a somewhat compound 
character of texture. There is a nearer approach to the fibres of animal life, each 
fibre being more distinct than those of any other internal viscus, and possessing a 
very delicate pencilling of transverse striae , as observed by Hodgkin and Lister. 
The fibres are only about one third of the magnitude of the animal fibre of the same 
subject ; they are interwoven with each other, and being more separable than the 
general fibre of the other organic viscera, project at the cut extremities, where their 
diameter is very apparent. The net-work which they form is composed of the entire 
fibre, and not, as in organic life in general, by the filaments of each. 
The examination of the pharynx, composed of the fibre of animal life, and that of 
the oesophagus of organic life, exhibited some views of considerable interest. This 
continuous line of tube commences in animal, and ends in organic fibre. I was de- 
sirous of ascertaining the nature of the junction, whether by a gradual blending of 
one description of fibre into the other, or by an admixture of the two. 
The constrictor superior, the first agent of deglutition, exhibits the perfect fibre of 
animal life. The striae are of ordinary size, of about 24 to the diameter of the fibre. 
Those of the constrictor medius exhibit no peculiarity, except that they are strongly 
marked and distinct ; but the cellular tissue is dense, possessing the character of 
that connecting the texture of organic life. The same observations will apply to the 
constrictor inferior, in which the density of the cellular tissue is yet perhaps greater. 
The structure of the first 2 inches and half or 3 inches of the oesophagus is that of 
animal life, but surrounded with striae varying much in number and in breadth. The 
size of the fibres themselves, likewise varies considerably, and may be found from that 
of the 700th to the 300th of an inch diameter (Plate XIX. fig. 1.). I have generally 
observed that the smaller fibres possessed the larger striae. These frequently ap- 
peared to bifurcate in their course around the tube, and at the edge distinctly pro- 
jected from the surface, forming the serrated appearance I have previously described. 
The larger the fibre the more delicate are the striae, which become less and less ap- 
parent on the larger fibres, as they descend on the oesophagus. Still the smaller 
fibre with large striae may be found as far as the fibre of animal life itself exists, and 
this junction of the two takes place at about 3 inches from the lower border of the 
constrictor inferior, where both structures are associated in the same object. One 
half inch below, and the fibre of animal life ceases entirely, and it is at this precise 
point that the oesophagus enters the cavity of the chest. 
Perhaps the most interesting, as well as the most instructive object exhibiting the 
muscular structure of organic life, is that of the arterial system, the composition of 
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