INTERRELATIONS OF THE MESONEPHROS, ETC. 181 



Weber, by whose paper Felix was admittedly influenced, brings 

 additional facts to bear on the case. He notes that in rodents 

 the embryos have either a small and short-lasting mesonephros, 

 as in the guinea pig and the mole, or small organs totally lack- 

 ing in the essential glomeruli, the tubules ending in blind en- 

 largements, as in the rat and the mouse. On looking for the 

 receptacle for the mesonephric urine, presumably the allantois, 

 he finds that it does not exist as an ehtodermal sac in some 

 rodents, and is always a slender tubular reservoir in man. He 

 reviews to a considerable extent the literature in regard to the 

 opening of the urogenital sinus, seeking a possible channel for 

 the urine into the amniotic cavity, and concludes, in spite of a 

 number of observations by others, which he quotes and which 

 place the date of this opening at various periods from 7.0 mm. to 

 as late as 20.0 mm., that this channel is not open in man until the 

 embryo has reached a length of 14.0 mm., whereas the mesoneph- 

 ros is apparently in full activity at 11.5 mm. "Sonach miiseten 

 wir uns zu der Annahme einer Sekretstauung in den ableitenden 

 Wegen mit all' ihren Folgen verstehen, oder wir mtissen, und 

 das ist wohl zweifellos das richtigere, auf die Annahme der 

 lebhaften absondernden Funktion verzichten."- This last argu- 

 ment is later discounted by Keibel, who says that though the 

 presence of well developed and numerous mesonephric glomeruli 

 does not show absolutely that the mesonephros secretes urine, 

 yet even if a very small amount of secretion were present, it 

 does not necessarily follow that the urogenital sinus must be 

 open at this stage, thus indicating his belief in the ability of the 

 human allantois, narrow as it is, to store a small amount of fluid. 

 Weber also lays stress on the interval between the beginning 

 of the progressive degeneration of the mesonephros and the 

 development of the kidney to a stage where it can be considered 

 functional, and accuses Nagel of disregarding this period in his 

 statement that both organs, the provisional and the permanent 

 kidney, are for a time active side bj^ side. The figures of 22.0 

 mm. for the beginning of involution of the mesonephros, and of 

 30.0 mm. for the development of the first renal glomeruli in 



- Weber, loc. cit., p. 67. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 19, NO. 2 



