The development of the kidney in the rahbit. 283 



The Balfour and Sedgwick view. 



The most commonly accepted view is that of Balfour and Sedgwick ^) 

 who are stated to hold the opinion that the convoluted tubules and 

 Bowman's capsules arise independently in the Kidney blastema and 

 join subsequently with the collecting tubules, which are themselves 

 branches from the Ureters. 



In Balfour's own words, p. 595. Vol. IL "A treatise on Compara- 

 tive Embryology", we find that "in the subsequent development of the 

 Kidney, collecting tubules grow out from the ureter and become con- 

 tinuous with masses of cells of the metanephric blastema, which 

 differentiate themselves into the Kidney tubules." 



It is here evidently implied that there are independent masses of 

 cells which are at first disconnected with, but which subsequently join 

 the collecting tubules. Every expounder of the Balfour-Sedgwick view 

 has accepted this interpretation of their results, in support of which 

 the following extracts from two of the most recently published works 

 on Embryology may be noticed: Oscar Hertwig-) says "The ureter 

 which has arisen from the end of the Wolffian duct grows into that 

 part of the middle plate which is located at the end of the Wolffian 

 body — one then sees that tortuous tubules become more and more 

 distinct in the small celled mass, and that in their walls malpighian 

 bodies are established. One finds further that there are evaginated 

 from the end of the ureter separate sacs which grow out into collecting 

 tubules, and probably later — certainty in regard to this has not yet 

 been established — join the tortuous tubules which have arisen in the 

 cortical part of the Kidney." 



Schäfer 3) states that "the convoluted tubules with their Mal- 

 pighian corpuscles, appear to be developed independently of the Ureter 



^) C. Emery, Recherches embryologiques sur la rein des mammifères. Arch, 

 italiennes de biologie. T. IV. p. 80 — 90 and Braun Inst. Würzburg. Vol. IV. 

 1877 likewise hold the primary formation of indépendant tubules and their sub- 

 sequent union with branches of the ureter. 



") Lehrbuch 1890. English Translation. 



•^) Embryology from Quain's Anatomy. Vol. I. Pt. 1. p. 122. 



