METABOLISM AND THE DISTRIBUTION OF MATERIAL 225 



pass through the walls. In general, however, it may be asserted 

 that the above explanation has brought no advance to our under- 

 standing of edema. Histologists and physiologists have contributed 

 an interminable amount of work without making any progress. 



A fundamental departure in the understanding of edema and its 

 associated questions was made in 1907 by the investigations of an 

 American, MARTIN H. FiscHER 1 , who sought the cause of edema, not 

 in the vessels, but in the tissues themselves; he attributes to the 

 edematous tissues an increased swelling capacity. M. H. FISCHER'S 

 views were immediately contradicted and led to more experimental 

 studies and scientific discussions than most biological theories. 

 However, though we must now admit that M. H. FISCHER'S 

 views are too far reaching, it cannot be denied that he set up a very 

 productive working hypothesis. We shall first state his theory and 

 then discuss his opponents' views. 



The most important experiment of M. H. FISCHER is the follow- 

 ing : he ligatures the hind limb of a frog so that its circulation is cut 



FIG. 39. Rabbit's kidneys; left normal, right experimentally edematous. 



off (Fig. 38) and places it in water so that the limbs are covered. 

 The ligatured limb swells up and at the end of 2 or 3 days may be 

 2 or 3 times its original weight. If the frog is kept in a dry vessel, 

 the ligatured limb dries up completely, and if it is cut off and placed 

 in water, it swells up. Under these conditions the blood pressure or 

 the increased permeability of the vessel walls cannot play any part 

 in the development of the edema, but it is only the tissues, which swell 

 more strongly under the circumstances mentioned. In the same 

 manner, M. H. FISCHER was able to demonstrate the occurrence of 

 edema in rabbits' kidneys (Fig. 39), and in the livers and lungs of 



1 He was led to this by experiments of JACQUES LOEB, which showed that 

 frogs muscles swelled more in acid and alkaline fluids than in neutral ones. 



