G. Carl Huber 11 



The outline drawings used in making- the models were sketched with 

 the aid of the camera lucida, a comjjaratively easy procedure for the 

 earlier stages, very time-consuming for the later stages, where constant 

 shifting of the field was necessary. The steps used in making the models 

 were those generally used when the Born wax-plate method of recon- 

 struction is employed. Special orienting planes or lines were generally 

 dispensed with, as it was found practicable to use for this purpose certain 

 prominent structures within the sections. The reconstruction of the 

 earlier stages of kidney development — the primary renal anlage and renal 

 pelvis with its primary branches, also the earliest developmental stages 

 of the uriniferous tubules — is a comparatively simple procedure. The 

 same can, however, not be said of the older stages and more fully 

 developed tubules. The complicated and varied arrangement of the 

 proximal and distal convoluted portions of the more fully developed 

 uriniferous tubules, above all the length of the loop of Henle make the 

 tracing of a single tubule through a series of sections a matter of difficulty. 

 However, on careful search through a series of sections, instances would 

 be found where one or the other arm of Henle's loop w^as cut through 

 nearly its entire length. By using this as a starting point, it was generally 

 possible to trace the remainder of the respective tubule. In doing so, it 

 was found helpful to make profile or temporary wax reconstructions of 

 certain parts of the tubule or to make temporary reconstructions of all the 

 tubules of a given area supposed to contain the portions of the tubule 

 sought and in this way separate it from surrounding tubules. After thus 

 mapping out a given tubule in its entirety, drawings were made which 

 could be used for reconstruction of the wdiole tubule. 



Anlage and Early Stages of Development of the Metanephros. 



The earlier stages of the development of the permanent kidney, the 

 anlage and early development stages of the renal evagination and of the 

 nephrogenic tissue (kidney blastema) shall here be considered very 

 briefly, since the appearance of Schreiner's contribution obviates the 

 necessity of a fuller discussion of this portion of my investigation, 

 i^either does it seem necessary to reproduce by way of illustrations the 

 numerous models made in the earlier part of this work showing shape, 

 size, and relationship of the renal evagination as found in the cat, rabbit, 

 pig, and man, nor to discuss the appearances presented by them during 

 the earlier developmental stages, since such figures w^ould in nearly 

 every instance duplicate the figures of similar stages given by Schreiner 

 (rabbit, text-figure 15-21 ; human, text-figure 26-27 ; pig, text-figure 29-30 

 of his article) based on profile and wax .reconstructions, except for the 



