Dr. Beale^ on Sarcolemma. 
103 
ON THE SARCOLEMMA OF THE MUSCLES OF INSECTS. 
As some of the most positive statements advanced respecting 
the arrangement of the nerves result from observations upon 
the muscles of insects^ I propose to consider the structure of 
the sarcolemma and its relation to the musclar tissue on the one 
hand^ and to the nerve-fibres and tracheae on the other, in this 
class. And in order that my observations may be the more 
easily tested by other observers, I select the muscles of an 
insect which can be obtained very readily in all countries and 
at almost every period of the year, viz., the common maggot 
or larva of the blow-fly. The specimens have been prepared 
according to the principles already laid down. 
Careful observation of the sarcolemma in this insect shows 
the existence of a number of transverse lines. These lines 
are not the transverse lines of the muscular tissue, but they 
are situated in the sarcolemma itself, as proved in specimens 
in which the sarcolemma has been torn away from the muscles. 
Not only so, but a thin layer, in which these lines may be 
discerned, may be torn from the surface of the sarcolemma, 
leaving the greater part of this membrane in its natural 
position. The distance which separates these lines from one 
another very nearly corresponds with that which intervenes 
between the transverse markings of the muscle, and for this 
reason they have escaped observation (PI. XV, fig. 9) . 
It will presently be shown that these transverse lines in 
the sarcolemma are produced by the ramification of fine 
branches of the tracheae. Nerves and tracheae in considerable 
number may be followed to the sarcolemma covering the 
muscle ; and when seen in profile, especially in the case of 
the nerve-fibres, a portion of the sarcolemma is drawn out, 
as it were, into a cone, the nerve, in fact, appearing to be 
connected with the summit of the cone. Such is the manner 
in which the Doyereschen nervenhugel of Kiihne result. 
Doyereschen nervenhiigel are represented in figs. 7 and 10. 
Now, in these cases one can often follow fine branches of 
the nerve-fibre from the point where it seems to pass into 
the Doyereschen nervenhugel for some distance over the 
surface of the sarcolemma. 
But, in order to demonstrate the highly elaborate arrange- 
ment of the nerve-fibres and tracheae of the insect-muscle, 
it is necessary that in a well-prepared specimen, the con- 
tractile tissue should be ruptured within the tube of the 
sarcolemma, and that the tube of the sarcolemma should 
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