STRIPED MUSCLE OF WASP 7 
to the appearance, rather than the intimate structure, of the 
muscle fiber and the sarcostyle. In referring to a disc, the term 
length (thickness) may be used to indicate the longitudinal 
extent, the term width (breadth) when speaking of the extent 
transverse to the long axis of the fiber. 
A system of indicating the several discs and membranes by 
letters has now been in general use since the time of Rollet’s 
earlier papers on striped muscle structure (85). These letters 
are the first of the respective German names designating the 
discs and membranes. If such a system is used at all, it seems 
better to retain that employed by Rollet. The only change 
that might possibly make any claim to effecting a gain would be 
the substitution of the letter “T’ to designate the telophragma, 
for the letter ‘Z’ (for Zwischenscheibe). ‘M’ could then continue 
to stand for mesophragma as well as for ‘Mittelscheibe.’ The 
terms telophragma and mesophragma (collectively inophrag- 
mata), proposed by Heidenhain, are so precise and convenient 
that their general adoption seems assured. The so-called ‘con- 
traction band,’ fundamentally a composite structure, is actually 
a contraction disc completed axially in cardiac muscle by the 
telophragma; and the so-called intercalated ‘disc’ is generally 
more nearly a band; that is, a peripheral portion of an earlier 
contraction disc. The intercalated dise is a more or less deeply 
extended band; or it may encircle the entire fiber in the formof a 
ring or perforated disc. It seems strange that the actual discs 
are commonly referred to as bands, and that the only structure 
that is not really a disc nevertheless continues to be designated 
‘intercalated disc.’ But long-continued, uniform usage has too 
firmly established these latter terms to warrant change at this 
time, especially in view of a prevailing sense of uncertainty 
regarding the complete history and intimate composition of 
these structures. 
Summarizing the foregoing suggestions, the parallel designa- 
tions of the principal discs and membranes, in terms of char- 
acters and abbreviations that best seem to commend themselves, 
are as follows (figs. 1, 2, and 10): 
