6 H. E. JORDAN 
or genuine elementary fibrils, they are conveniently designated 
metafibrils. However fitting the term sarcolemma would be for 
designating the membranous envelope of the sarcostyle, this 
word should probably be retained in the sense of referring to the 
cell membrane enveloping the smooth muscle cell, or the myo- 
blast, or the definitive striped muscle fiber taken as a whole. 
For the envelope of the sarcostyle, I would suggest the term 
sarcostylic membrane. In macerating fluids and under mechan- 
ical stresses the sarcostyle becomes broken up at definite levels 
into regular segments, the sarcomeres (inokommata). These are 
bounded terminally by definite membranes, the telophragmata 
(Krause’s ground membranes, Dobie’s lines, intermediate mem- 
branes). The telophragmata are continued into the intersar- 
costylic fluid spaces and serve to bind together the adjacent 
fibrils of a muscle fiber. Each sarcomere contains a median 
darkly colored, more deeply staining, dark disc (dim disc, trans- 
verse disc of Briicke, sarcous element of Bowman). This dark 
dise is under certain conditions bisected by a light median disc 
(Hensen’s disc), which is in turn bisected by a delicate mem- 
brane, the mesophragma (median membrane of Heidenhain). 
Between the terminal telophragmata and the median dark 
dise lie the light discs (clear discs, intermediate dises of Krause, 
hyaline substance of Schaefer). In insect leg muscle the light 
dises are frequently bisected, or crossed close to the telophrag- 
mata, by a delicate, dark, granular disc, the accessory disc (dise 
of Merkel and Rollet). Under these circumstances, the portions 
of the light dises between the terminal telophragmata of the 
sarcomere and the accessory dises are designated the end discs 
(dises of Englemann). 
This condition of stratification of chemically and physically 
different substances within the sarcostyles gives to the fiber, 
when viewed under low magnification, a striped or banded ap- 
pearance, a light ‘band’ alternating regularly with a dark ‘band.’ 
It is obvious, however, that we are actually dealing with discs 
(and membranes), not with genuine ‘bands’ or ‘stripes.’ But 
the designation ‘striped’ or ‘striated’ may continue to be em- 
ployed rather than the more precise term ‘stratified’ as applying 
