58 



Development and Shape of Urinifcroiis Tubules 



given in the figure, the loop of Henle grows down in front of the 

 Malpighian corpuscle and the first portion of the proximal convoluted 

 tubule belonging to each tubule. Thus these conform to the general 

 law as previously stated. In each of the two tubules which develop in 

 connection with the posteriorly placed end branches, while these hold 

 the position given in the figure, the loop of Henle grows down behind the 

 Malpighian corpuscle and the first portion of the proximal convoluted 

 tubule. If now the whole configuration as shown in the figure be turned 

 through an arc of 180°, thus bringing the two posteriorly placed tubules 

 in front, these will show the same arrangement and relations of parts 



Fig. 12. Semidiagrammatic figure given to show the relations the urini- 

 ferous tubules bear to the collecting tubules and end branches as observed a 

 short time before the middle of embryonic life. Not all the uriniferous tubules 

 would show in such a configuration about the same degree of development as 

 here represented, c, collecting tubule; e, end branch of collecting tubule; a, 

 ampulla; vi, Malpighian corpuscle; n, neck; pc, proximal convoluted tubule; 

 pi, proximal or descending limb of Henle's loop; al, ascending or distal limb 

 of Henle's loop;dc, distal convoluted tubule; ;, junctional tubule. 



as was shown by the two tubules which previously occupied the anterior 

 position; that is to say, the loop of Henle now passes down in front of 

 the IMalpighian corpuscle, while in the other two tubules, those which 

 previously held the anterior position and now occupy a posterior position, 

 the loop of Henle now passes down behind the Malpighian corpuscle. 

 In stating, therefore, the general law that the loop of Henle in its 

 development and elongation passes down in front of the Malpighian cor- 

 puscle and the first part of the proximal convoluted tubule, cognizance 

 must be taken of the relationship of a given uriniferous tubule to the 

 collecting tubule in which it ends. The first part of a proximal con- 

 voluted tubule, beginning with its attachment to the Malpighian corpus- 



