W. W. SWINGLE 513 



the larvae died, and it was impossible to keep them alive long enough 

 to see whether the wound would have healed, leaving the ducts 

 functional. 



It was observed during the course of the experiments that the on- 

 set of the edema appears to be coincident with the opening of the 

 Wolffian ducts into the cloaca. It is at about this time also that 

 the yolk mass begins to undergo rapid resorption. Apparently water 

 is not rapidly absorbed through the integument until the yolk mass 

 undergoes considerable diminution. 



In this connection, it was suggested by Professor McClure that 

 the onset of edema in the nephrectomized larvae should coincide with 

 the initiation in the embryonic body of a continuous lymph flow 

 through the lymphatics, between the periphery and the veins, since 

 the attainment of this condition presents the first opportunity for 

 water, absorbed through the skin and taken up by the lymphatics, 

 to reach the kidneys by way of the lymphatic and blood vascular 

 systems. This condition is established normally in frog and toad 

 larvae, according to McClure,^ at about the time when the intestine 

 has differentiated out of the yolk mass, and the yolk has undergone 

 resorption. I feel sure that the onset of edema occurred at about 

 this time in the nephrectomized frog larvae. 



The extirpation experiments recorded here show that any mal- 

 functioning of the kidney, any block in its excretory canals, or com- 

 plete loss of function, as for instance in nephrectomy, leads to an 

 excessive accumulation of fluids in the lymph sinuses, tissues, and 

 body cavity. They therefore confirm in a striking manner the re- 

 sults obtained by McClure and, as far as the Anura are concerned, 

 it can now be regarded as an established fact that edema may arise 

 from a block in kidney function. 



I wish to acknowledge my indebtedness to Professor McClure for 

 many helpful suggestions and for the interest he has shown in the work. 



^ McClure, C. F. W., On the behavior of Bufo and Rana toward colloidal dyes 

 of the acid azo group. Memoirs of The Wistar Institute of Anatomy and Biology, 

 No. 8, Philadelphia, 1918, 48; On the provisional arrangement of the embryonic 

 lymphatic system, Anat. Rec, 1915, ix, 281. 



