350 DK D. BERKY HART. 



penetrate the bladder wall after passing inside the lateral 

 canals ; the central vaginal canal lies between them. 



Lister and Fletcher figure a diagram of an early foetus of 

 Macropus rufus, and state that the ureters pass outside both 

 Miillerian and Wolffian dusts, an arrangement, they say, like 

 that of the adult didelphys. There must be some error here, as 

 whatever view one takes of the origin of the vaginal canals in the 

 opossum, the ureters pass to the inner side of the lateral canals. 



The question of these relations has now to be raised in regard 

 to the human fretus. Here we get opinions at variance with 

 what I find in the specimens I have examined, Nagel says : 

 " The ureters lie to the outside of the Wolffian ducts " (in foetus 

 of 8 mm.). 



In an embryo figured by Keibel from His' collection (embryo 

 L.O. 25 mm., female, 8i-9 weeks), Keibel states that the ureters 

 lie lateral, the Wolffian and Miillerian ducts mesial. A section 

 of this is figured, and also serial sections to illustrate the rela- 

 tion (figs. 90-100, Keibel). An examination of these (Keibel, 

 pp. 100 and 103) seems to me to bear a different interpretation. 

 Fortunately the foetus of which I figure transverse sections is 

 about the same age and size as L.O., and is practically the same 

 in structure. 



From the study of these and a third specimen, which I owe 

 to the kindness of Mr Stiles, the following seems to me a more 

 correct view. 



(1 ) At the genital cord, where in the human foetvis the Wolffian 

 ducts are placed together, with the blended and therefore now 

 single Miillerian ducts between, tve get the ureters lateral. One 

 cannot compare the foetus at this level with the adult kangaroo 

 type, as the canals are too approximated. 



(2) Higher up in the foetus we get the following relations — 

 viz., to the outside, the Wolffian duct ; somewhat internal to this 

 the Miillerian duct, and much further towards the middle line 

 the ureters {v. fig. 90 of Keibel.) As one passes down the 

 sections the Wolffian and Miillerian ducts lie closer together, 

 and the ureters are thrown to the outside. The bladder is high, 

 however, in the kangaroo — i.e., lies in front of the cornua ; in 

 the human female it is deeper ; the ureters, therefore, enter 

 the kangaroo bladder higher up. 



