Dr. Beale, on Barcolemma, 
95 
legists. But as the difficulty of determining these essential 
points is very greats and as some of the appearances seen 
could be accounted for in several different ways, many 
conflicting accounts of the arrangement have been given, and 
are now entertained and taught by different authorities. 
The consideration of the nature and mode of formation of 
the sarcolemma involves the discussion of the relation of the 
nerves and vessels to the contractile material of striped 
muscle; and though the question is anatomical, it has a 
physiological bearing of the utmost interest and importance. 
Sarcolemma is even more distinct, and certainly more readily 
demonstrated, in the muscles of many insects than in those of 
vertebrate animals. 
Sarcolemma not constantly present. — This membrane is not 
to be demonstrated in connection with all the elementary 
fibres of striped muscle in vertebrate animals, and it would 
therefore appear that sarcolemma was not essential to the 
growth, development, and formation of muscular fibre ; nor 
can it be a structure necessary to the due performance of the 
function of this highly elaborate form of contractile tissue. 
Sarcolemma cannot be demonstrated upon the muscular fibres 
of the heart nor upon those of the tongue. In the auricle of 
the frog^s heart, in the lymphatic hearts and in the tongue of 
the same animal, the striped muscular tissue forms in many 
places a sort of web of exceedingly fine fibres, many being so 
fine that they are not wider than the very fine fibres or fibrillse 
into which an elementary fibre of the limbs, for example, may 
be split up. Now, it is most certain that these very fine fibres 
are not enclosed in a tubular membrane, as may be proved 
most distinctly in many of those cases in which the fine 
fibres taper into tendons. Moreover, there are many other 
localities in the frog in which very distinct and narrow 
elementary fibres may be demonstrated, in which no tubular 
sarcolemma can be detected — for example, in the small 
muscles of the eyelids and eyeball, in parts of the mylo-hyoid 
of the green tree frog, and in young muscles of the limbs. 
Character of sarcolemma. — Of the existence of such a 
tubular membrane, however, in many cases there is not the 
least question. It is a tube often firm and of measurable 
thickness, with nuclei in connection with it. It is as clear 
and positive as a kidney-tube from which the epithelium has 
been washed out. Generally, the tube of sarcolemma is very 
firm and most distinct in old elementary muscular fibres of the 
muscles of the limbs and those which possess two distinct 
points of attachment ; but in these I have noticed that while 
the structure is distinct in the case of the old and fully 
