THE GLOMERULI AND TUBULES 723 



glomeruli by way of a small vessel connecting the capillary 

 plexus round the tubules and the vas afferens of the glomerulus, 

 so that within a short time of ligature 50 per cent, of the 

 glomeruli might be in circulation again. 



Owing to the crucial importance of these experiments, further 

 investigation has been carried out by several observers, all of 

 whom appear to have been satisfied with the accuracy of their 

 anatomical basis ; but the grounds of their satisfaction have not 

 been in all cases convincing. Beddard agreed with Nussbaum 

 that, when all the arteries supplying the kidneys were ligatured, the 

 glomeruli were permanently out of circulation and no spontaneous 

 secretion of urine took place. He found that it was a matter of 

 some difficulty to ligature the whole arterial supply of the kidneys, 

 and that by merely observing that a given frog secreted no urine, 

 spontaneously, it is impossible to say that the ligature was com- 

 plete and all the glomeruli out of circulation ; in fact, that it was 

 impossible to say this unless the kidneys had been injected and 

 serial sections cut. He did not confirm Nussbaum' s other 

 results. For, he never found that injections of urea could bring 

 about a secretion of urine after a complete ligature. But this 

 result is not necessarily in opposition to Nussbaum, for none of 

 Beddard' s injections were made until two days after the ligature, 

 at which time he found that a rapid degeneration of the tubule 

 cells set in. And there is nothing to show whether the 

 failure of urea in his experiments to set up a secretion was due 

 to the ligature being really complete or to the tubules having 

 begun to degenerate. Mosberg obtained results which resemble 

 closely those of Nussbaum. He found that the ligature prevents a 

 spontaneous secretion of urine ; that in ligatured frogs injections of 

 dextrose cause no secretion, but simultaneous injection of dextrose 

 and urea produce a flow of urine which does not contain sugar, 

 while injections of phloridzin alone lead to glycosuria. The injec- 

 tions were made directly after the operation, but the experiments 

 are not conclusive in that he did not control the completeness of 

 the ligature by a microscopical examination of the kidneys. Halsey 

 has confirmed Nussbaum' s results even more fully. He found 

 that ligatured frogs excreted urea and indigo- carmine in their urine, 

 but not dextrose, egg albumin, peptone, and carmine. He showed, 

 like Mosberg, that phloridzin can still produce glycosuria after 

 the ligature, and added that the same was true of simultaneous in- 

 jections of theobromine and dextrose. Halsey does not mention in 



