Nature of the Muscular Contraction. 91 
with the first two salts, and well marked with the others, partic- 
ularly with iodide and sulphocyanate. Frog's gastrocnemii 
immersed for five minutes in m/8 Nal or m/S NaCNS show rapid 
contraction and twitching when immersed in isotonic solutions 
of the following substances in Ringer's solution or physiological 
salt-solution: saponin, digitalin and solanin (marked action); 
agaricin and aconitine (relatively slight action) ; chloroform (marked 
action); Na-oleate (marked action); bile-salts (marked action); 
horse and dog serum (marked action with vigorous twitching); 
tetanus toxine (vigorous twitching); rattlesnake venom (mod- 
erate action). The intensity of the stimulating action shows a 
general parallelism with that of the hemolytic action. 
Muscles may be similarly sensitized to osmotic stimuli (dis- 
tilled water and hypertonic sodium chloride solution). This fact, 
as well as the fact that colloidal substances (serum, etc.) may show 
marked stimulating action, furnishes additional proof that stim- 
ulation depends essentially on an alteration of the plasma mem- 
brane. 
54 (579) 
Nature of the muscular contraction. 
By E. B. Meigs, 
[From the Wistar Institute of Anatomy and Biology.] 
The comparison of histological preparations of uncontracted 
and contracted smooth muscle indicates that during the contrac- 
tion of this tissue fluid passes from the fibers to the interstitial 
spaces. It seems possible, therefore, that the contraction of 
smooth muscle may be brought about by an interchange of fluid 
between its cells and their surroundings in the same way that the 
movements of Mimosa are caused by changes in the turgor of 
its cells. This hypothesis may be tested by investigating the effect 
of swelling reagents and their opposites on the length of smooth 
muscle. The hypothesis would be supported if it could be shown 
that smooth muscle lengthened when immersed in solutions which 
cause it to gain in weight and shortened in the opposite class of 
solutions. 
The changes of weight and the changes of length of frog's 
smooth muscle have been followed in Ringer's solution, in various 
