472 STUDIES IN GENERAL PHYSIOLOGY 
preceding chapter in such a way as though Van’t Hoff’s 
theory of osmotic pressure did not hold for physiology, these 
experiments might perhaps teach him better. 
This is especially the case with reference to the experi- 
ments with MgCl,, CaCl,, SrCl,, and BaCl,. One mol. 
of these compounds was dissolved in one liter of distilled 
water and then diluted to the same degree as a 0.7 per cent. 
NaCl solution. A muscle was introduced into 100 c.c. of 
each of these solutions. Table XIV gives the weight lost in 
these solutions in one hour. 
Each of the salts mentioned here dissociates into three 
ions—two electro-negative chlorine ions and one bivalent 
electro-positive ion. According to this, the relation of thenum- 
ber of molecules actually present to those originally present 
isas[N(1—a)+3Na]:N=1+2a. a in this case= 
0.6 —0.7. 
TABLE XIV 
| I | II | Average 
MgCl, .......... —3.3¢| —3.7¢| —3.5¢ 
GaClonceccccess —3.4 | ~3.5 | —3.4 
SrCloi.coss ciaas —3.3 —4.7 —4.0 
BaCly........... —5.1 | -6.7 | —5.9 
Without dissociation the osmotic pressure of each of these 
salt solutions would have amounted to 2.67 atmospheres. In 
consequence of the dissociation the osmotic pressure rises to 
2.67 (1 + 1.3) = 6.14 atmospheres. 
The loss in weight which the muscles suffered in these 
solutions is nearly equal to the loss in weight which the 
muscles suffered in a 1.05 per cent. NaCl solution. In the 
latter solution this amounted on the average to 3.8 per cent. 
The osmotic pressure of such a solution is about 7.3 per cent., 
that is, therefore, a little higher than that of the MgCl, 
solution. When we consider, however, that the condition of 
Digitized by Microsoft® 
