Muscuuar TWITCHINGS 759 
tive to stimuli which normally would not affect these organs. 
For example, when we put a fresh muscle for one or more 
minutes into a % solution of sodium citrate, a peculiar 
form of irritability arises (contact-irritability)." Whenever 
the muscle is taken out of the solution it goes into powerful 
tetanic contractions, which cease at once and give way to 
relaxation of the muscle as soon as the latter is put back into 
the solution. When this hypersensitive condition is once 
established, the contractions can be produced whenever the 
muscle is changed from any aqueous solution to any other 
non-aqueous medium, while the contractions cease when the 
muscle is put back into an aqueous medium,no matter whether 
the latter be a solution of an electrolyte or a non-conductor. 
It is rather striking that these phenomena do not occur when 
the above-mentioned solutions call forth at once the rhyth- 
mical contractions mentioned in the previous part of this 
paper. It almost looks as if there existed two allotropic 
states of the muscle substance, the one giving rise to rhyth- 
mical twitchings, the other to the peculiar tetanic contrac- 
tions (contact-reactions) just referred to.’ Ultimately, how- 
ever, in all cases, rhythmical twitchings are produced. 
As far as motor nerves are concerned, I have shown in 
the same paper that the same salts which produce this con- 
tact-reaction produce hypersensitiveness of the nerve and 
ultimately rhythmical contractions of the muscle when acting 
upon the nerve alone. 
It might be mentioned here in parenthesis that these facts 
may throw some light upon the action of cathartics. All the 
salts which give rise to the above-mentioned contact-reaction 
or hypersensitiveness act as cathartics when introduced into 
the intestine. The common explanation of their action is 
1Part II, p. 692. 
2This difference is emphasized by the fact, found by my pupil, Dr. Zoethout : 
that an addition of potassium favors the contact-reaction. As far as rhythmical con- 
tractions are concerned, K has an inhibiting effect. 
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