24 H. E. JORDAN 
Menten, in her extension of the experiments of Macallum, 
has shown that the chlorides, the phosphates, and the potassium 
salts have an ‘analogous distribution.’ And her beautiful 
colored illustrations show clearly that these salts change their 
position during contraction, and that this change of position 
corresponds closely with the transfer of the deeply staiming 
substance from the dark dise of the relaxed fiber to the con- 
traction band of the contracted fiber. Accordingly, there occurs 
during contraction a reversal of striae as regards these salts as 
well as regards a possibly specific substance of the dark disc. In 
full contraction these salts are segregated practically within the 
limits of the contraction band (Menten’s figs. 17, 18, 22, 26, 31, 
36, and 38). The conclusion is suggested that the deeper color 
and the deeper staining reaction of the Q dise and of the con- 
traction band are actually due, at least in part, to the segregation 
of these salts within these levels at the functional stages of 
relaxation and contraction. 
In figure 8 is reproduced a photomicrograph, from Meig’s 
paper,” of a living contracted sarcostyle of the wing muscle of 
the fly, mounted in a medium of equal parts of white of egg and 
a 2 per cent sodium-chlorid solution. The contraction bands 
are conspicuous. The sarcomeres have lost approximately half 
of their length and attained approximately double their diameter, 
as compared with the relaxed fiber. At a the contraction bands 
appear single, at b double. Meigs interprets the double con- 
dition as an optical illusion’due to the oblique orientation of the 
sarcostyle at b. However, the contraction band is by virtue of 
its origin essentially a double structure, comprising principally 
two halves of adjacent dark discs. It seems to me more probable 
that these apparently double contraction *bands in this illus- 
tration should be interpreted as incompletely fused contraction 
bands. In spite of the sharp lateral contour of this contracted 
sarcostyle, clearly shown in the figure, Meigs nevertheless inter- 
prets such fibrils as slightly beaded,, with constrictions at the 
levels of the telophragmata (contraction bands); an assumption 
required by the imbibition hypothesis of contraction, but in 
contravention of microscopic data. 
