8 H. E. JORDAN 
Telophragmane 47.10 pepe ta eee ee Por) 
LightdisG). 022 eee. Cee ee tee en J 
Darlkidisé <7) Sree Cee ee aN Q 
Mediancdise . sccye meena eta acct hak sate H 
Mesoplirae ina siarras ris cer he eee, ha) M 
ACCESSORVMGISG ARS Sida, Seemann. N 
NY 6 Race st Cpe he sha ty MOM ae ARC rs RED Lea ce E 
Contractionndises(band).. 3.0. se mea oe ane CB: 
Interealatedsband (disc) me. £.) ease oe Lele): 
IV. REVIEW OF LITERATURE 
For the purpose of putting into sharper relief the central 
points at issue, it seems desirable here to review the literature 
and to appraise the illustrations bearing directly on the sig- 
nificance of the contraction band of functionally contracted 
muscle, and on the question of the similarity of this band to the 
simplest type of intercalated disc. 
The most satisfactory figure illustrating the changes in striped 
muscle during contraction is that by Rollet” of a fixed and 
stained lateral contraction wave in the leg muscle of the chry- 
somelid beetle, Cassida equestris (fig. 1). At the right the fiber 
is said to be in extension; at the left, under Doyere’s hillock, in 
the fully contracted condition. Contraction involves a move- 
ment of the separating halves of the dark discs in opposite direc- 
tions and a fusion of the approaching halves of adjacent dark 
discs about the telophragma. This fusion involves also the in- 
tervening accessory discs. The result is a deeply staining con- 
traction band, comprising one telophragma, two accessory discs, 
and two opposite halves of adjacent dark discs. There has 
occurred, accordingly, a reversal of striations during contraction 
as regards a deeply staining substance located in Q and N in 
the extended condition and transferred to the contraction band, 
originating about the telophragma, in the contracted condition. 
Rollet??* agrees with the earlier conclusion of Merkel (’72) 
that the moving substance in contraction is the anisotropic 
constituent of the sarcostyle. Rollet’s figures” of similar 
fibers, as viewed under crossed nicols, show all of the deeply 
