48 H. E. JORDAN 
by use of Rollet’s gold-chlorid technic. We have already shown, 
however, that Schaefer, as a matter of fact, confused an arti- 
ficially swollen condition of the fiber, resulting from the action 
of the hypotonic formic-acid-water solution of this technic, with 
a condition of functional contraction. The assumption that the 
darker quality of the dim disc of striped fibers is wholly the 
results of the segregation of anisotropic materials within the 
general limits of this disc under certain conditions has led to 
much confusion, and has introduced an element of unnecessary 
difficulty in interpreting the morphologic changes suffered by a 
striped muscle fiber during contraction. 
Moreover, undue emphasis upon the presence of anisotropic 
materials in this contractile tissue has influenced some of the 
leading theories of contraction culminating in Englemann’s hy- 
pothesis‘ that contraction is essentially a matter of the absorp- 
tion of isotropic by the anisotropic material. However, the 
presence and segregation of specific anisotropic materials cannot 
_ be held responsible for the dark color of the ‘dim’ dise in un- 
stained fibers; nor are such alleged anisotropic materials properly 
interpreted as the substance which takes the stain in the dark 
dise in stained preparations. ‘The dark disc is the result of a 
substance apart from, and in addition to, the alleged anisotropic 
materials. The striping of the wing-muscle sarcostyles of the 
wasp and other insects is quite as definite, if not more so, both 
in the unstained and stained condition, as in the leg muscle; 
yet only in the latter material can the stratification of the aniso- 
tropic substance under certain conditions be clearly demon- 
strated with the micropolariscope, while in the former it is 
present in so small amount as to be practically impossible of 
demonstration in the single sarcostyle. The substance that 
moves during contraction in the formation of the contraction 
band is this additional deeply staining material. I have con- 
vinced myself by a study of the leg muscle of the wasp that the 
anisotropic material (condition) as segregated in the relaxed 
fiber is not shifted into the light (J) dise during contraction. It 
is also clear, however, that the anisotropy of the fiber is greatly 
lessened by contraction. This latter fact is emphasized also by 
Meigs." 
