STRIPED MUSCLE OF WASP 3 
be able to add support to McDougall’s theory by his data from 
a detailed microscopic study of the sarcostyle of the wing muscle 
of the fly. These investigators advocate a close parallel between 
the phenomenon of muscle contraction and the swelling and con- 
sequent shortening resulting from endosmosis; and between 
relaxation and the reduction of swelling and the consequent 
lengthening resulting from exosmosis. 
Englemann‘ claims to be able to demonstrate by means of the 
micropolariscope that the anisotropic substance, which he re- 
gards as constituting the ‘dim’ band, does not change its location 
during contraction. Schaefer, by means of Rollet’s gold-chlorid 
technic, claims to have proved the same fact. Schaefer, ac- 
cordingly, identifies the substance which stains with gold chlorid 
with the anisotropic material of the sarcoplasm. The earlier 
investigations of Merkel,!? Rollet,22 and Tourneux,*® on the con- 
trary, seemed to demonstrate a reversal of striae during con- 
traction. These investigators claim that the anisotropic sub- 
stance of the ‘dim’ band of uncontracted muscle divides along 
the mesophragma and moves in opposite directions toward the 
terminal telophragmata of the sarcomere to form the anisotropic 
contraction bands of contracted muscle. Contraction is by them 
conceived to be the result, or at least an accompaniment, of the 
movement of anisotropic materials from mesophragma to telo- 
phragma, producing thus a reversal of striations. No attempt 
is made to explain the fundamental relation between this move- 
ment of the anisotropic constituent of the sarcoplasm and the 
coincident contraction of the sarcostyle. Rutherford?* also con- 
cludes for a reversal of striation during contraction, and identifies 
the ‘chromatic element’ (dark disc) of the sarcoplasm with the 
anisotropic substance. 
The phenomenon of contraction, as expressed primarily in the 
formation of a contraction band, has become intimately related 
to the question of the significance of the intercalated discs of 
cardiac muscle. It is now clear that none of the earlier hypoth- 
eses which interpreted these dises as intercellular cement lines, 
tendons, or developing sarcomeres are any longer tenable. Ina 
series of papers I have developed the hypothesis that the inter- 
