94: Development and Sliape of Uriniferous Tubules 



distance, Ix't'ore ri>ai'liin^u' tlie eoUecting tubule, presents an epithelium 

 wliicli is like that of the snuill collectiii<;' tubules. This short segment 

 may be spoken of as belonging to the collecting tubule or with ec|ual pro- 

 priety as forming part of the uriniferous tubule proper, as it is difficult 

 to state with any degree of certainty whether it develops as an outgrowth 

 of the collecting tubule or is differentiated with the other parts of the 

 uriniferous tubule from the renal vesicle. 



Before giving by way of a diagram or scheme the shape of a urinifer- 

 ous tubule and its relation to a collecting tubule, as this presents itself 

 to me, brief mention may yet be made of a number of diagrams of urin- 

 iferous tubules found in the literature, each of which presents certain 

 characteristics which make it different from the others selected. These 

 I have grouped under Fig. 23. The different conceptions of the form of 

 a uriniferous tubule held by the authorities presenting the diagrams here 

 given and their departure from the conception of the form of a urinifer- 

 ous tubule as presented in Fig. 24 may be most readily expressed in this 

 graphical manner. 



In A^ Schweiger-Seidel's diagram, is given inaccurately the relative 

 position of the Malpighian corpuscle and proximal and distal convoluted 

 portions, more especially the distal convoluted portion which is separated 

 too much from the proximal convoluted portion. In B, Von Ebner's 

 diagram, an attempt is made to bring the distal convoluted portion in 

 relation with the Malpighian corpuscle (accepting Hamburger's obser- 

 vations) and to show that the first part of the proximal convoluted por- 

 tion extends toward the cortex (Golgi). The diagram presents inaccura- 

 cies in the relations given to the Malpighian corpuscle and the proximal 

 and distal convoluted portions. In C, Haycraft's diagram, of a urin- 

 iferous tubule of a rabbit, he presents, as is obvious, deductions drawn 

 from the study of a tubule showing an early stage of development, shown 

 in his Fig. 10. This, as I have stated, very probably presents parts of 

 two tubules, there sketched as one. His diagram is wrong in the position 

 given to the Malpighian corpuscle and as to the length, shape, and 

 relative position of the proximal and distal convoluted portions. D, one 

 of Golgi's figures, shows a uriniferous tubule at a relatively early stage of 

 development. This is not a diagram, but the figure is introduced, since 

 it shows quite correctly the relations of the different parts of a uriniferous 

 tubule. E, Disse's diagram, one of the most recent at hand, gives incor- 

 rectly the relations shown by the ascending and descending limbs of 

 Henle's loop to the Malpighian corpuscle and the course of the first part 

 of the proximal convoluted portion. F, Stoerk's diagram, based on recon- 

 structions of uriniferous tubules, presents a number of inaccuracies, as is 



