6 Dovelopinont and Sliapo of Urinifernus Tubules 



states that so far as his own observations go. he is inclined to accept a continuous 

 epitlieiial aniage of the uriniferous tubules as given l)y Minot and Nagel ; lie does not, 

 however, desire to commit liimself until he himself has made further investigations. A 

 number of excellent illustrations are found in this chapter. 



Disse, who discusses briefly the development of the kidney in his account of the 

 anatomy of the urinary organs as given in I5ardele))en's Ilandbuch, states that as a result 

 of his own observations made on guinea pig and pig embryos, he is led to conclude that 

 both the straight and the coiled uriniferous tubules have the same anlage, namely from 

 the hollow liuds of the primitive kidney pelvis. The selection of the section which forms 

 the basis for his Fig. 77, showing the anlage of the coiled uriniferous tubule seems to 

 me unfortunate. The S-shaped portion (anlage of the coiled tubule) is not cut through 

 the center of its lumen, only a small part of which is seen in the figure. The appar- 

 ently continuous structure as represented might, it seems to me, be simulated by an 

 overlapping of the two bevelled surfaces of two discontinuous structures (anlage of 

 coiled tubule aud collecting duct), especially as the section from which the drawing 

 was made seems to luxve been relatively thick. 



Haycraft's contribution to the development of the kidney of the rabbit may yet 

 receive consideration as his observations have been widely accepted. He states that 

 " the tubules and Malpighian bodies arise as buds of solid cells from the wall of the 

 primary renal vesicles " (ampullar enlargement of the primary divisions of the renal 

 anlagej " close to the cortex. The bud makes a double bend like an 8, first turning 

 with a large sweep away from the vesicle, then turning toward it and sharply away 

 again. The basement membrane can be traced along it and a central lumen forms almost 

 to its tip." Ilaycraft also traces the development of these S-shaped buds into the 

 uriniferous tubules and gives his conception of the form of such a tubule as present in 

 the adult kidney of rabbits. The figures accompanying this article are of special interest 

 to me, since my series of sections of rabbit embryos of various ages as also numerous 

 reconstructions of uriniferous tubules made from the same, aflford a basis for their inter- 

 pretation. His Fig. 8, ■■ A high power view of the first formation of a urinary tubule 

 from a primary, renal vesicle " represents, I fear, a much older stage, only a portion 

 of this tubule being shown in the section sketched. His Fig. 10, I interpret as embracing 

 parts of at least two tubular anlagen, there sketched as one tube, owing to the position 

 given to the glomerular anlage with reference to the other portions of the tube. Furtlier 

 reference to this article will be made later. 



Brief mention may yet be made of the conclusions reached by a number of observers 

 who have investigated the development of cystic kidneys. Hildebrand suggested that 

 the want of union between the collecting tubules and the anlagen of the uriniferous 

 tubules was the cause of the cysts of the congenital cystic kidney, in that, when this 

 condition obtains, as " the glomeruli begin to functionate there is no opportunity for 

 the outflow of the secretion and consequently the tubules are expanded into cystic 

 structures." Ribbert, who describes observations made on a cystic kidney of a new-born 

 male child, was able to show that many of the cysts were developed from Malpighlan 

 corpuscles which showed no connection with collecting tubules, the ends of certain of 

 which were also cystically enlarged. Meyer found in microscopic sections of the kidneys 

 obtained from a !)-weeks-old female child, which showed other congenital defects, cer- 

 tain regions where the kidney parenchyma was normally developed and other regions 

 where collecting tubules and Malpighlan corpuscles were observed, but where the tubular 

 portions of the uriniferous tubules which normally unite these structures are wanting 

 and in place of which there was observed " an undifferentiated tissue rich in cellular 

 elements in which the cells only in certain regions were arranged in the form of rings 

 or cords." These observations, it appears to me, confirm in a satisfactory way the con- 

 clusions of observers, who recognize separate anlagen for the collecting tubules and the 

 uriniferous tubules proper. 



From this brief summary of the literature, it may be seen that the controversy found 

 in the early literature concerning the origin and development of the coiled portion of 

 uriniferous tubules of the permanent kidney is still found in the more recent literature, 

 the weight of evidence, however, being on the side of a discontinuous origin of the 

 coiled portion of the tubule, as Felix has very recently correctly stated. 



This investigation was begun in the spring of 1902. In considering 

 the possible sources of error of other investigators who have dealt with this 

 subject, it occurred to me that the thickness of the sections studied 

 might alone be responsible for a certain per cent of the discrepancies 

 found in the literature. The average thickness of serial sections of 

 embryos used in embryological investigations is seldom below 10 /x,, more 

 often perhaps 20 (x. My own observations soon convinced me that 



