G. Carl Huber 5 



nriniferinis tiilniles. I regard it as a distinct aohievenicnt on his part to be alile to 

 trace tlie close relationship between the mesonephrogenic tissue from which are devel- 

 oped the mesonophric tnl)ules. the sei)arate aniage of wliicli is generally accepted, and the 

 metanephrogenic tissue from whicli are developed the seci-etory i)ortions of the uriniferous 

 tubules of tlie permanent kidney. As is no doul)t evident, the nephrogenic tissue here 

 referred to has lo!ig been known as the renal blastema : there are, however, various opin- 

 ions regarding its origin and its share in the development of the kidney. I shall have 

 occasion to make further reference to this excellent article of Schreiner. 



Herring, in a very creditable contribution based on observations made on material 

 derived from human emliryos. was first led to believe tliat the kidney tubules were 

 branches of the collecting tubes, but " could never find the early stages, which should 

 have been easily seen if that view were correct." He further states that " in the thick 

 layer of the capsule, cells are seen which show a gradual transition in appearance from 

 embryonic connective tissue cells to a character resembling that of the epithelial cells of 

 the early convoluted tubules. Between these cells and those of the ampullae " (dilated 

 ends of the collecting tubes) " there is always a distinct line of separation and in the 

 majority of instances there is a space where the tubule has shrunk during the process 

 of hardening. The careful examination of serial sections has convinced me that these 

 masses of cells which appear under the capsule and in the interlobular septa, are quite 

 independent of the ureter branches and give rise to the Malpighian bodies, convoluted 

 tubules and Henle's loop, uniting always with short branches from the ampullae." 



Hamburger's paper, based largely on investigations made on the kidneys of mouse 

 embryos and young mice, contains important data concerning the later stages of the 

 development of the uriniferous tubules and the development of the Malpighian pyramid. 

 His observations are based on serial sections and on what must be regarded as very suc- 

 cessful preparations made by maceration and teasing. He makes only incidental mention 

 of the origin of the uriniferous tubules, which he regards as developing from small 

 bodies (Korperchen), the smallest of which are spherical cell groups which have only an 

 apparent connection with the enlarged distal ends of the collecting ducts. 



Haugh, in one of the most recent contributions to the subject, in which he presents 

 observations made on an extensive material derived from human embryos of all ages, 

 gives a full account of the development of the pelvis of the kidney and of the shape of 

 the pelvis of embryonic and adult kidneys, based on metal injections and on wax recon- 

 structions. He also presents data concerning the lobulation of the human kidney and 

 on the development of the collecting tubules. He treats, however, very superficially — to 

 use his own words — the earlier stages of the development of the uriniferous tubules, 

 allying himself with those authors who defend a separate anlage of the uriniferous 

 tubules. 



Stoerk, on the other hand, defends the older view of the development of the uriniferous 

 tubules. According to this observer, the renal anlage, derived from the Wolffian duct, 

 grows dorsally and, after repeated dichotomous division, meets the anlage of the renal 

 capsule which retards the further radial growth of the tree-like branches of the renal 

 anlage. Each of the branches now develops an ampullar enlargement at its extremity, 

 which later assumes a heart-shape. Each half of the heart-shaped enlargement buds out 

 laterally and forms a short tube, the whole structure now assuming the appearance of 

 a Y. Each arm of the Y-shaped termination then divides dichotomously. the one branch, 

 which for a time remains small, passing toward the periphery, the other, which grows 

 more rapidly, budding and growing toward the stem of the Y. The Y-shaped structure 

 now presents the appearance of an inverted anchor. The points of this anchor-shaped 

 structure now grow in such a manner as to assume the shape of an S. Such an S-shaped 

 structure is an anlage of a uriniferous tubule and of Bowman's, capsule. Stoerk's more 

 recent contribution contains only a brief statement concerning the anlagen and early 

 developmental stages of the uriniferous tubules and this is merely a reiteration of the 

 views presented in his earlier jjaper. In this second paper. Stoerk gives the results of 

 observations made on serial sections of material derived from human embryos and 

 numerous wax-reconstructions made therefrom. These reconstructions represent mainly 

 the earlier developmental stages of the uriniferous tubules, a fact which is no doubt re- 

 sponsible for certain errors which he has committed, in using the data gained by a study 

 of the earlier stages to interpret the shape and structure of more fully developed 

 tubules. As I shall have occasion to refer frc(iuently to this paper in connection with a 

 discussion of my own results, its further consideration may here be dispensed with. 



Gerhardt, who has recently published, from t). Ilertwig's laboratory, also defends the 

 view that the uriniferous tubules are developed l)y budding and that the permanent 

 kidney is an organ nui r/cneris. As material, he used largely mouse embryos, but also 

 those of chicken, dog. and pig. Gerhardt's article is concerned largely with a discussion 

 of the literature and with theoretic speculations. His own observations are very 

 briefly given and. as il'ustratidiis are wanting. ma.\ be summarized l)y giving one of his 

 conclusions: "The peripliei'al portions of the uriniferous tuliules arise through a con- 

 tinuous growth of the collecting tubes. It cannot be demonstrated that in the cortex 

 formed tubes make secondary connection with the tubules of the medulla." The capsule 

 of the glomeruli he regards as an invagination of the distal end of the uriniferous 

 tubules. 



In Chapter IV ( Entwickelungsgeschichte und Missbildungen der Nieren) of Vol. 52b, 

 Deutsche Chirurgie (Kiister, Krankheiten der Jviere), written by Strahl, this observer 



