76 CHRISTIANNA SMITH 
recommended by Huber (’09) have been used in this paper. 
The parts of the tubule and the kinds of epithelium are, briefly, 
as follows: First, comes the renal corpuscle with its double- 
walled capsule of flat epithelium. Continuous with the epi- 
thelium of the outer wall of the capsule is the short, often indis- 
tinct, neck which unites the capsule with the first portion of the 
tubule, the proximal convoluted tubule with the medullary 
segment. The epithelial linings of the proximal convoluted 
portion and the medullary segment are essentially the same 
throughout. The high cells, with striated free border, indistinct 
cell boundaries, and rodded protoplasm of the basal portions of 
the cell are all distinguishing features. The medullary segment 
of the proximal convoluted portion is followed by that part of 
the tubule known as the loop of Henle, but for which Huber 
suggests the name, medullary loop. The parts of this are the 
proximal or descending limb, the distal or ascending limb, and 
the crest. The epithelium of the descending limb is of a thin 
pavement type, with relatively large nuclei, which reach from 
the top to the bottom of the cell and may cause the cell to bulge 
into the lumen. The crest of the loop may be formed either by 
the thin descending limb, if the loop is long, or if it is short, by 
the thick ascending one. The ascending limb extends to the 
renal corpuscle of its own tubule, and is followed at that point 
by the distal convoluted portion, which extends to the collecting 
tubule. Policard (1213) states that the type of epithelium 
characteristic of the ascending limb is continuous in the distal 
convoluted tubule, and Huber does not believe the variations 
which may be present in the different parts great enough to 
warrant the recognition of other types. Huber, however, con- 
siders the epithelium as low, columnar, with indistinct cell 
boundaries, granular protoplasm, indistinct basal striations, and 
as possessing no striated free border. In his work on Batrachian 
and mammalian specimens (’04, 710, 712), Policard points out 
that this segment possesses very thick rods or batonnets, which 
extend from the base of the cell to the edge bordering the lumen, 
a characteristic which has been found true in the forms studied 
during this work. A discussion of this type of epithelium will 
