LIPOID CONTENT OF THE KIDNEY TUBULE 83 
Ten per cent formalin and scarlet red. Very large globules 
which were present in the cells stained with scarlet red in all of 
the tubules of the cortex. 
Ten per cent dichromate and sudan III. Just as in the kitten, 
those granules which stained deeply with scarlet red and black 
with osmic acid were not preserved by this method, and the 
cortex appeared as if composed of vacuoles. The lipoids in the 
descending limbs of the medullary loop, in the ascending limb, 
and the collecting tubules did stain, however, and this showed 
that the non-preservation of the fat in proximal tubules was not 
due to poor preservation (fig. 10). The cells of the medullary 
segment of the proximal convoluted tubules were desquamating 
and stained diffusely with red, no lipoid droplets being present. 
The appearance of the very fat kidney differed, then, from 
a kidney with the rayed appearance of the cortex in that all the 
tubules were very full of large lipoid granules and the lower 
portion of the medullary rays did not contain lipoid droplets. 
Benda’s fluid. In fluids containing osmic acid, the cortex was 
blackened intensely (fig. 8). All the tubules were affected 
except portions of the medullary rays. These tubules, the 
medullary segments of the proximal convoluted tubule, whose 
cells were desquamating, did not blacken, and the limbs of the 
medullary loop and collecting tubules contained very fine granules. 
A linear arrangement of these could often be seen. In a section 
fixed in Benda’s fluid and stained in anilin acid fuchsin, the 
granular appearance of the mitochondria, and rods of the ascend- 
ing limb of the medullary loop stood out very clearly. 
The cortex of the kidney of a very fat 184-cm. kitten looked 
more like the cortex of the kidney of a fat cat. The proximal 
convoluted tubules in the labyrinth contained fine and moderately 
coarse granules, while the medullary rays and medulla were 
unstained (figs. 3 and 4). 
A free-hand section of the kidney of a foetal cat which had 
been preserved in formalin several months was stained with a 
fresh solution of sudan III and found to be abundantly supplied 
with lipoid granules. 
