LIPOID CONTENT OF THE KIDNEY TUBULE 75 
solutions employed which depended on the presence of the 
dichromate with further mordantage in a simple solution of it, 
for the preservation of lipoids, were Helly, Zenker, modifications 
of them, and Regaud’s fluid. Bell’s (14, ’15) acidified 10 per 
cent potassium dichromate was used and kept at a temperature 
of 51° for forty-eight hours. The fixers which contained osmic 
acid were Flemming’s and Benda’s fluids, and a solution of 10 
per cent potassium dichromate and 2 per cent osmic acid. 
In preparing material for fixation, it was found best to use both 
radial and tangential sections, cut from 1 to 2 mm. in thickness, 
in order that the preservation of the lipoids would be as complete 
as possible. Lipoids which reduced osmic acid were found to 
be kept best if the imbedding were done in parlodion according 
to Kingsbury (711). More stainable lipoids with better preser- 
vation were found after fixation, in a solution of potassium 
dichromate and osmic acid. The results obtained were practi- 
cally the same whether heat was employed or not, so that it 
seems clear that the results were due to the combination of the 
dichromate and osmie acid. 
Free-hand sections of fresh material were stained in an alkaline 
alcoholic solution of scarlet red (Bullard, 712, 713), which both 
Bell and Bullard consider the most efficient stain for the demon- 
stration of fat granules in fresh or frozen sections. One per cent 
osmic acid was also used. In the fixed material, absolute alcohol 
was avoided throughout the work. Sudan III and hematoxylin 
were used as stains after Bell’s dichromate fixation, iron hema- 
toxylin and copper hematoxylin after dichromate fixations such 
as Zenker and Helly, and anilin acid fuchsin and hematoxylin 
after osmic acid solutions. 
MORPHOLOGY OF THE URINARY TUBULE 
In the study of the lipoid content of the kidney, it was found 
that a knowledge of the parts of the renal tubule with their 
characteristic kinds of epithelium was necessary in order to 
rightly interpret the distribution of the lipoids and their relation 
to the tubule, and, further, to avoid any ambiguity. The terms 
