WatTeER ABSORPTION BY MUSCLES AND Soaps 513 
The analogy between the behavior of soaps and of muscles 
is of importance for the mechanics of the absorption of 
liquids. The majority of authors—for example, Hofmeister 
—assume that in the absorption of liquids by tissue we 
deal with imbibition; that is to say, with capillary phe- 
nomena. In the absorption of water by soaps, however, we 
deal with phenomena of solution." The forces concerned in 
the latter are osmotic pressures, and not surface tensions, as 
in capillary phenomena. 
The antagonism which has been shown by these experi- 
ments to exist between potassium and calcium compounds is 
of interest in another direction. Ringer has called attention 
to the fact that an antagonism exists between calcium and 
potassium salts in their effect on the heart. The latter are 
supposed to favor the diastole, the former the systole, of the 
heart. Howell has adopted the views of Ringer. Possibly 
the above-described characteristics of the two substances may 
help to explain the phenomena of contractility. I cannot 
assent to the view that calcium is the “stimulus” for the 
cardiac activity. Years ago this might have been errone- 
ously said about oxygen. The cause of cardiac activity (as 
that of every automatic activity) is neither calcium nor oxy- 
gen, but heat, or, more correctly, its intensity factor, tem- 
perature. Calcium and potassium might be of importance 
for the changes in the amount of water in various elements, 
or for their state of matter, and so be of importance for the 
contraction of the heart. 
II 
I had shown in my earlier publications that when a trace 
of acid is added to a 0.7 per cent. NaCl solution, a muscle 
immersed in it absorbs a large amount of water.’ I was 
1This statement will probably have to be modified. Sinee water can be removed 
from soaps by pressure, it is at least partly held there by imbibition. [1903] 
2“ On the Physiological Effects of Ions,’’ Part IJ, pp. 450 and 501. 
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