0. C. Farrington — Tfie Nephrostomes of Rana. 313 



just above the kidney before injection of the carmine. It was hoped 

 thus to determine whether the carmine would enter the circulation 

 through other vessels, if it were not supplied by the kidneys. Upon 

 examination the particles were found to have entered the nephro- 

 stomes only a little way, and were not present in any of the blood 

 vessels ; but, as the stopping of the circulation caused the animal to 

 die veiy quickly, the test was not regarded decisive. 



It seems probable that if the nephrostomes connect with the blood 

 vessels they would be reached by injections of the latter. As no 

 mention is made by other writers of experiments of this kind, except 

 that of the injection of the ureters by Haslam, this point was care- 

 fully tested. The first injection was made through the vena cava 

 inferior, the anterior abdominal being also opened. This showed 

 only the blood vessels to be injected and no passage of the fluid into 

 any of the nephrostome tubes. The second injection was made in 

 the same way except that the renal-portal of one side was tied so 

 that if any extra pressure were needed to force the fluid into the tubes 

 it might be thus supplied. The results were, however, like those of 

 the first injection. The third injection was made through the renal- 

 portal of a very large frog with the anterior abdominal opened. By 

 this means the nephrostomes were successfully injected, the fluid show- 

 ing plainly in the tubes and funnels and even coming to the surface, 

 though it did not flow out to any extent. This result seems to place 

 the connection of the nephrostomes with the blood vessels almost be- 

 yond question. On seeking, however, to trace the direct opening of the 

 nephrostome tube into a blood vessel by means of sections, it w^as found 

 as before impossible to do so with absolute certainty, though the con- 

 nection was in many cases very close. Since the nephrostomes prob- 

 ably serve as lymph vessels, the openings into the capillaries must be 

 small enough to prevent the passage of the blood corpuscles into them, 

 so that, as before stated, the chances of tracing them with certainty 

 are few^ indeed. The experiments seem to teach that the passages 

 inward from the nephrostomes can be reached by a current going 

 toward the vena cava but are closed to one coming from it. This is 

 difficult to explain if true, but needs further proof. The remarkable 

 change of function which the nephrostomes seem to undergo, from 

 service as excretory organs to that of lymph vessels, gives rise, also, 

 to physiological questions of much interest. It is not, however, the 

 purpose of this paper to discuss these, since they call for much fur- 

 ther investigation. It is the hope of the author that others may 

 study these points and bring new facts to light. 



