466 STUDIES IN GENERAL PHYSIOLOGY 
A comparison of Tables XII and XI shows again how 
much stronger the specific effect of the hydroxyl ions is than 
that of the hydrogen tons for the absorption of water by 
muscle. 
The increase in the weight of the muscle under the influ- 
ence of dilute acids and alkalies therefore continues even 
when the muscle has already lost its irritability. As only 
small amounts of the acids and alkalies are used, one is 
inclined to imagine the effect of the H and OH ions to be of 
a fermentative character. 
vy. IN HOW FAR ARE THE CHANGES IN THE WEIGHT OF THE 
MUSCLE A FUNCTION OF DIFFERENCES IN OSMOTIO PRES- 
SURE BETWEEN THE MUSCLE AND THE SURROUNDING 
LIQUID ? 
1. I have availed myself of more than a hundred experi- 
ments to show that in a 0.7 per cent. NaCl solution the 
gastrocnemius muscle of the frog generally suffers no impor- 
tant change in weight during the first hour. Often it loses 
a few milligrams in weight; in rare cases it increases a trifle; 
in the remaining cases its weight remains absolutely con- 
stant. The 0.7 per cent. NaCl solution can therefore be 
looked upon as approximately of the same osmotic pressure 
as the total osmotic pressure of the molecules and ions dis- 
solved in the muscle cells. The fact that the presence of an 
acid or base in the salt solution compels the muscle to increase 
in weight shows that we have to deal in living matter with a 
system which alters its osmotic pressure easily, or in which 
the permeability of the protoplasmic wall is easily modified;' 
One might perhaps think at first that the great increase in 
the weight of the muscle upon the addition of acids or alka- 
lies is simply determined by the fact that the muscle itself 
1It is possible that the absorption of water caused by alkalies and acids belongs 
to those phenomena of imbibition which have recently been studied by van Bemmelen. 
[1903] 
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