STRIPED MUSCLE OF WASP 51 
relatively greater, producing a constriction, in the Q-disc, and 
tension resulted first in an elongation of the Q-dise. Since 
isotropy is the result of the orientation of the molecules of a 
substance in the same axial direction (Ranvier), we should 
expect this optical condition accentuated in that portion of the 
fiber, namely, the more fluid Q portion, where the molecules or 
particles were relatively more free to orient themselves (during 
relaxation) in the axis of stress, that is, parallel to the longitudinal 
axis. The corollaries to this explanation are: 1) that the disturb- 
ance of this identical orientation of the particles of the Q-disc 
during contraction resultsin a greatly lessened or a vitiated isotropy 
of the fiber and, 2) those relaxed fibers which are in an appar- 
ently inactive condition as regards especially stratification, may be 
such in which the particles of the Q-disc have not yet become 
reoriented in the longitudinal axis immediately after contraction. 
The reversal of striae, however, as seen in unstained and 
especially in stained fibers is a function of a substance unrelated 
fundamentally to the anisotropic phenomenon, and is the result 
of the change in position during contraction of some other than 
a specifically anisotropic substance from the vicinity of the 
mesophragma to the vicinity of the telophragmata. Reversal of 
striation, as regards a deeply staining substance, and con- 
traction are coincident phenomena. No doubt a causal con- 
nection exists, but a description of the fundamental nature of 
this connection awaits further study. The phenomenon of re- 
versal of striae, and the chemical constitution of the deeply 
staining substance involved, are conditions obviously more 
closely related to contraction than the very widespread (or- 
ganically and inorganically) condition of isotropy. Any final 
and adequate explanation of contraction must be able to em- 
brace the fundamental morphologic datum of an intrasarcostylic 
reversal of striation as regards the deeply staining substance of 
the sarcoplasm during contraction. 
e. Contraction and the contraction band 
We are not here concerned with the formulation of a new 
theory of muscle contraction. Our primary purpose is to 
