8G Dcvclojimcnt and Shape of riaiiifi'i-oiis Tuhnlcs 



puscle, one coil or lonp iieiierally restin<;- upon it. The upper end of 

 the distal arm of tlio h)op of Henle remains from the time when it may 

 he first recognized in close relation to the Malpighian corpuscle, either 

 passing over it at a variable distance from the origin of the proximal 

 convoluted ])ortion or crossing this near the corpuscle. Hamburger, 

 who has also observed this close relation of the ascending limb to the 

 corpuscle, states that in a number of his preparations showing various 

 stages of development, he found the upjier end of the ascending liml) of 

 the loop of Henle in close relation with the Malpighian corpuscle and 

 in the region wliere the vessels enter and leave it. This, he states, is 

 readily explained when it is remembered that the loop of Henle is orig- 

 inally in the bowl of the " pseudoglomerulus," therefore in contact with 

 the developing glomerulus ; and as the loop grows in a central direction, 

 the Malpighian corpuscle is fastened to this region by means of capil- 

 laries from the vas efferens. Golgi is quoted as saying (Stoerk) that it 

 is the thin arm of the loop which is fastened to the corpuscle in the 

 region of vessel exit. I agree with Stoerk in saying that neither the 

 proximal nor distal arm shows any definite relation to the vessel porta 

 of Bowman's capsule. That, however, especially the ascending limb 

 of the loop returns for each tubule to the coil complex formed by proxi- 

 mal and distal convoluted portions into the immediate vicinity of its 

 ^lalpighian corpuscle is clearly shoA\'n by all my reconstructions as 

 well as those of Stoerk, as also the tubules obtained by maceration by 

 Golgi and Hamburger, retaining thus in later stages of development and 

 in post-foetal life the relations shown in early stages of development. I 

 have not satisfied myself that the relations become fixed through the 

 agency of arterioles or capillaries, branches of the vas efferens, nor by 

 an especial development of interstitial tissue in this region, although 

 the latter factor seems now and then to play a role. The descending 

 limb of Henle's loop in the region where it leaves the coil complex is 

 generally in close relation with the upper end of the ascending liml). 

 sometimes lying to the inner side of it, again over it, therefore also near 

 the Malpighian corpuscle, showing in this respect also in later stages 

 of development the relations borne in early stages of its evolution. The 

 two limbs of Henle's loop are generally quite parallel and take quite a 

 direct course toward the apex of the INfalpighian pyramid. Certain of 

 the loops — those belonging to the tubules which are first developed — 

 extend to near the pelvic epithelium, the apex of the pyramid, retaining 

 in this respect the relations shown in early stages of development, elon- 

 gating as the medulla develops. Tubules of the several generations 

 which develop later terminate at various levels in the medulla and, in 



