LYMPH FLOW 35 



excess of fluid contained in the body has been deposited as 

 lymph in the tissues and cavities of the body, and not as urine 

 in the cloaca and intestinal canal. Therefore, only by ligating 

 the ureters can a typical oedematous condition of the body 

 be produced. 



It has previously been observed by a number of writers 

 that living frogs, as well as toads, lose weight when sus- 

 pended in hypertonic saline solutions. We are now in a posi- 

 tion to compare the behavior of a living frog whose ureters 

 have been ligated with that of a skin glove filled with Ringer's 

 solution isotonic with frog's blood, when each is suspended 

 in a hypertonic solution. In the case of the living frog, with 

 ureters ligated, the conditions are essentially analogous to 

 those in the skin glove; each consists of a closed sac of frog's 

 skin. In the experiment about to be mentioned and in others 

 similar, the cloacal opening was ligated in addition to the 

 ureters. This was done to insure against the fluid's escaping 

 from the body in case an extravasation should occur at the 

 point where the ureters had been ligated. The ligation was 

 accomplished by passing under the ureters a silk ligature 

 which was tied over the urostyle. The cloacal opening also 

 was tied with a silk ligature. It is no easy matter in all cases 

 to get what one may regard as a satisfactory ligation ; injury 

 to the skin by the needle is very likely to permit lymph in the 

 dorsal subcutaneous lymph sinuses to extravasate through 

 the openings. Unless the ligation is practically perfect, the 

 frog or toad should not be used for experiments of this char- 

 acter. Better results have usually been obtained on frog's 

 recently caught than on those which have remained for some 

 time in the laboratory. This seems to be due to the fact that 

 in pale-skinned winter frogs the skin is much thinner and 

 is more easily injured than in those recently captured. On 

 account of the toughness of their skin, toads have generally 

 been found to be more favorable subjects for these experi- 

 ments than are frogs. 



In the following experiment (344, fig. 14) a living frog, 

 with its ureters and cloacal opening ligated, was fastened to 



