G. Carl Hiiber 51 



Brief mention may yet lie made of tlie conclusions reached by former observers who 

 have considered the genesis of the different parts of the uriniferous tubules. Toldt, 

 who was the first to recognize clearly the S-shaped stage in the development of the 

 uriniferous tubule, a stage in which the anlage is spoken of as a pseudo-glomerulus, 

 does not give a clear account of the anlage of the tubular portion. I find in his 

 account the following statement, which I shall give in his own words : " Bemerkens- 

 werth ist feruer, dass die Windungen des Caniilchens constant den der Nierenoberfliiche 

 zugewendeten. iiusseren Theil des Pseud'igloniorulus einiiehmon. wiihrend das schalen- 

 formige Ende des Canalchens stets in dem Abschnitte desselben gelegen ist, welcher 

 nach dem Innoren der Nicre zn sielit.'" (Page 134.) This statement taken in con- 

 nection with Toldt's account of the development of the Malpighian corpuscle, I in- 

 terpret as meaning that he regards Bowman's capsule (and glomerulus) as developed 

 from the lower curve of the S-shaped structure while the remaining parts of the 

 uriniferous tubules are developed from the tubular portion of rhe " p^eudoglomerulus " 

 and not. as is now and then stated, that Toldt regards the S-shaped tubules (pseudo- 

 glomeruli) as merely the anlagen of the Malpighian corpuscles. Haycraft, in his 

 account of the anlage of the diflei'ent parts of the uriniferous tubule, makes reference 

 to a figiire (Fig. 8 of his article), which he describes as "a high power view of the 

 first formation of a urinary tubule from a primary renal vesicle," which flsiire I have 

 interpreted as showing only a portion of a tubular anlage. He states that " each 

 little sprout from a renal vesicle will, in other series of older embryos, be seen to 

 elongate, the bulging portion marked H will grow down toward the primary pelvis to 

 form the convoluted tubules and the loop of Henle, the part at in marks the formation 

 of the future Malpighian body." The bulging portion marked H as shown in his 

 figure refers to the region of the junction of the S-shaped tubular anlage with the 

 ampulla of the collecting tubule, m marks the end of the tubule as seen in the figure. 

 Golgi's account of the development of the uriniferous tubules, elucidated by his well 

 known semidiagrammatic figures of developing icnal tubules of mammals is here given as 

 presented by Minot (Page 510), leaving out the reference letters. "The different 

 parts of the S-shaped tubule have each their fixed destiny. The end of the S (in the 

 diagrams the lower part) receives the vascular loop, which gives rise to the blood- 

 vessels of the future glomerulus ; the lower limb of the S elongates enormously and 

 forms the first division of the convoluted tubule including the loop of Henle; the upper 

 limb of the S also elongates very much — though less than the lower limb — and is the 

 anlage of the second division of the convoluted tubule ; where the two .loin, the tubule 

 passes close to the Malpighian corpuscle and seems to be intimately attached to it." 

 Except perhaps for the fact that I have differentiated more clearly the different parts 

 of a tubular anlage of an S-shape and am thus able to give more explicitly the genesis 

 of the different parts of a uriniferous tubule, my own account mav be considered 

 as confirming Golgi's account as here given. Hamburger states that the first portion 

 of the coiled uriniferous tubule to differentiate (leaving out of consideration Bowman's 

 capsule) is the loop of Henle, which has its anlage in that portion of the S-shaped 

 tubule which is taken up by the bowl-shaped anlage of Bowman's capsule ("welche 

 eigentlich durch die von der Schale aufgenommene Riegung des S-formigen Caniilchens 

 vorgebildet ist"). The portion which extends into the concavity of the lower S-curve 

 in the region of the junction of the upper S-curve and S-middle piece, which I 

 have also regarded as the anlage of the loop of Henle (I am not certain that I have 

 interpreted the above statement of Hamburger correctly, as the account is not quite 

 clear to me). He also states that the distal convoluted portion (Schaltstiick^ is 

 differentiated early, before the proximal convoluted portion (Tubulus contortus) 

 has acquired any coils. The latter portion, he states, is developed from the third, 

 the most distal liml) of the S-shaped tubule. It should be recalled that Hamburser 

 recognizes in the S-shaped stage (pseudoglomerulus) a bowl-shaped structure and an 

 S-shaped tubular portion (see page 36 of this article) much as described hv Stoerk 

 for his secondary S-stage. Hamburger, in speaking therefore of the third or distal 

 limb of the S-shaped tubule refers to the curved tubular segment which is in continuity 

 with the anlage of Bowman's capsule ; this would represent the tubular segment which 

 develops from the region of the junction of the lower S-curve and S-iiiiddle piece, 

 which I have also regarded as the anlage of the proximal convoluted portion. Schreiner 

 recognizes in the S-shaped tubular anlage essentially the same regional differentiation 

 leading to the formation of the different parts of the uriniferous tubule as given by 

 me, as may be seen by a study of his Fig. 114. to which especial reference is made in 

 his account. Stoerk's oljservntions on the mode of formation of the different parts of 

 the uriniferous tubules need to be considered somewhat more fully, as he is the only 

 one of previous workers who has made extensive Ufe of reconstiuction methods in 

 the study of the subject. It will be remembered that he recognizes a primary and 

 a secondary S-stage in the development of the uriniferous tubules. As the Malpighian 

 corpuscle completes its development, the S-shaped tubule of the secondary S stage 

 elongates and acquires from four to five " short, plump windings." The epithelliim 

 of the tubular portion, which up to this stage, has shown the same structure throughout, 

 now shows a differentiation, beginning with the attachment of the tubule to the outer 

 layer of Bowman's capsule and extending for one to two windings of the tubule. 

 The cells here obtain more protoplasm, wliicli becomes clearer and the nuclei assume 

 a basal position. This cell-differentiation, as described by Stoerk, both as to the time 

 of its appearance and as to the region of the tuliule affected is about as given by me. 

 .\bout this time, there develops from the coiled tulmlar portion a loop which grows 

 downward over the Malpighian corpuscles to form the loop of Henle. Concerning the 

 location of this loop. Stoerk has this to say: I use his own words: " Es liisst sich 

 von vornherein durchaus nicht sagen, welche von den urspriinglich untereinander 

 ganz gleich aussehenden Windungen zu diesem Anwachsen zur Schlinge bestimmt ist. 

 solange in alien das Kpithel ein dunkles ist : erfahrungsgemiiss ist es meist die zweite 

 nach dem Abgang vom Malpighischen Korperchen." That the portion of the tubule 



