8 CHARLES F. W. MC CLTJRE 



been taken up and held by the muscle tissue. An explanation 

 of the process by which this has come about constitutes, in 

 the frog at least, the problem of intracellular (interstitial?) 

 oedema. Two leading theories have thus far been advanced 

 in explanation of the causation of this form of oedema. These 

 are the osmotic pressure theory, as advanced by J. Loeb 

 ( '98), and the colloid-chemical theory of Martin Fischer ( '15). 



We may state at the beginning that an experimental analy- 

 sis of the conditions found in the frog decidedly indicates 

 that the production of the intracellular (interstitial?) form 

 of oedema is owing to differences which can be demonstrated 

 to exist between the osmotic pressure of the oedematous 

 lymph in the subcutaneous lymph sinuses and hence in the 

 blood plasma, and that of the lymph in normal muscle tissue. 



Let us first consider different experiments made upon the 

 same living frog placed in water after the osmotic pressure 

 of its body fluids has been raised beyond a point we may 

 ordinarily regard as normal. We know that when a normal 

 frog remains out of water for a considerable time, or is placed 

 in a hypertonic saline solution, a loss in body weight follows 

 owing to a loss of water from the body. When such a desic- 

 cated frog is placed in water, immediately it begins to gain 

 in weight, and continues to do so until water has been driven 

 by osmosis through the integument into the subcutaneous 

 lymph sinuses sufficient in amount to restore the osmotic 

 pressure of the body fluids to a point that may be regarded 

 as normal. When this condition has been established, the 

 normal frog either begins to lose in weight or else for a con- 

 siderable time remains stationary; from this time on, how- 

 ever, it never gains weight continuously. Three experiments 

 of this character — experiments in which the same frog, after 

 desiccation, was successively placed in water at 17°, 23°, and 

 32° C. — are illustrated by curves 1, 2, and 3 in figure 1. The 

 broken lines in the figure indicate the loss in body weight 

 which resulted during the period the frog remained out of 

 water; and the continuous lines, the subsequent behavior of 

 the frog when placed in water. Such curves, denoting the 



