282 J- B- Haycraft, 



for preparations of the embryo chick at several stages of development. 

 At a time when I had no laboratory of my own, Professor Schäfer 

 placed his at my disposal, and I have to thank him for much advice 

 and help ungrudgingly given during my stay in London. The work 

 was carried out during part of my tenure of the Eesearch Scholarship 

 of the British Medical Association. 



Early Development of Kidney. 



It is generally accepted that the Kidneys arise at the distal ends 

 of the Ureters, which tubular structures have previously budded off as 

 branches from the Wolffian Ducts. In the rabbit at the eleventh day 

 of embryonic life, Kolliker describes the ureters as passing away from 

 the Wolffian ducts, and ending in the masses of cells from which the 

 Kidneys arise. This mass of cells, called the Kidney blastema, is a 

 portion of the intermediate-cell-mass, which shifts its position until it 

 lies above and behind the Wolffian body. Beyond this point we 

 cannot pass without encountering strongly conflicting opinion, and this 

 is especially the case when we examine the descriptions given of the 

 origin of the Kidney tubules, the all important structures found within 

 this gland. 



The Origin of the Kidney Tubules. 



Eemaki), Kolliker ^), Löwe^), and others state that the tubules 

 arise as branches from the ureters, and that these grow into the 

 Kidney blastema, dividing again and again. According to this view 

 it will be seen that the Kidney developes on much the same general 

 plan as the lung, the liver or other secreting glands, and that the 

 epithelial elements of the tubules and Bowman's capsules are further 

 developments of, and actual descendants from the epithelium of the 

 Wolffian ducts, while the mesoderiïïiil tissue of the Kidney blastema 

 contributes to the organ its connective- tissue framework and blood- 

 vessels. 



') Quoted by KiJlliker. 



-) Entwickehingsf^eschichte <les Mensolien und der i.'öheren Tiere. 1879. 



') rentralblatt f. d. Med. Wiasenschaft. Oct. 1879. 



