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STUDIES IN GENERAL PHYSIOLOGY 



preceding chapter in such a way as though Van 't Hoffs 

 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 2 , Ca01 2 , SrCl 2 , and Ba01 2 . 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 the num- 

 ber of molecules actually present to those originally present 

 is as [N (1 a) + 3Na] : N = 1 -f 2a. a in this case = 

 0.6-0.7. 



TABLE XIV 



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 g 

 solution. When we consider, however, that the condition of 



