, CHARLES F. W. McCLURE 267 



The experiments clearly show when the ureters are completely 

 ligated and the toad is placed in water, that an increase in body 

 weight immediately takes place which gradually progresses into an 

 intense form of generalized edema. An analysis of the conditions 

 described nee^d not be given here, further than that the progress of 

 the edema appears to be related to the extent and character of the 

 abrasion produced in the tissues at the point of ligation, as well as 

 upon the state of congestion of the tissues which results from ligation. 



On the basis of these observations it does not appear difficult to 

 explain the edematous condition of the frog larvae mentioned above. 



We know that the glomeruli of the pronephros are not directly con- 

 nected with the renal tubules, as is the case in the meso- and meta- 

 nephros, but project into the body cavity independently of these 

 tubules in the vicinity of the nephrostomes. The filtrate of the 

 pronephric glomeruli must necessarily, therefore, pass into the body 

 cavity before entering the pronephric tubules by way of the nephro- 

 stomes. If, on account of a deficiency in their development, the 

 tubules of the pronephros should be unable to take care of all the 

 glomerular filtrate, or to secrete fluid obtained .from the pronephric 

 veins, an excess of fluid which could not be eliminated by the kid- 

 neys would necessarily remain in the body cavity and tissues and, in 

 the course of time, would increase in amount so that a typical edema- 

 tous condition of the body would finally result. Such I believe to be 

 an explanation of the edematous condition observed in these frog 

 larvffi. 



Further significance of the above observations lies in the fact that 

 they do not appear to bear out Fischer's^ view that the cause of 

 edema, in the anura at least, resides in the tissues, and is due to an 

 overproduction or accumulation of acids within the body which 

 causes them to take up water. It has also been pointed out by vari- 

 ous authors^ that this view is untenable on account of the limited 

 variation of the hydrogen ion concentration in the body. 



^ Fischer, M. H., CEdema and nephritis, New York, 2nd edition, 1915. 

 ® Henderson, L. J., and Cohn, E. J., /. Am. Chem.Soc, 1918, xl, 857. Crozier, 

 W. J., /. Biol. Chem., 1916, xxiv, 255, 443; 1918, xxxv, 455. 



