LIPOID CONTENT OF THE KIDNEY TUBULE (3 
larger grains exist at the periphery of the section which he con- 
siders badly fixed mitochondria. These flakes and granules 
which Policard describes are quite clearly lipoids in combination 
that are stained by the mitochondrial technique which he used. 
Evidently Policard does not take into consideration the fact that 
in the preservation of lipoids the best fixation of a mass of tissue 
is at its periphery, while at the center of the mass the fixation 
may be incomplete. In discussing other portions of the tubule, 
Policard mentions that lipoids are rarely found in that portion 
which corresponds to the ascending limb of the medullary loop 
(loop of Henle). 
MaceNider (716, 718), in his work on nephropathic dogs, refers 
to the presence of fat in the ascending limb of the medullary loop 
as of frequent occurrence. 
In his investigation of the fat infiltration of the cat’s kidney, 
Mottram (’16) observes that lipoids are present in the convoluted 
tubules and rarely in the straight tubules. He checks up in 
this paper, an observation made by Leathes, that the lipoid 
content of the cat’s kidney, instead of being more unsaturated 
than that of of the liver and ‘lipoid tissue,’ as it is in the kidneys 
of other animals, man, dog, goat, pig, is sometimes more saturated 
than ‘lipoid tissue’ and never as unsaturated as that of the liver. 
HISTOCHEMICAL CHARACTERISTICS 
The observations made by Bell in his several papers in regard 
to the histochemical properties of lipoids may be tabulated as 
shown on page 74. Most of these observations were made in 
the study of muscle, but they are applicable as well to lipoids in 
the kidney. Fats that are solid at ordinary room temperature 
do not form any part of the stainable substance, although such 
fats may be present in small quantity. 
MATERIAL AND METHODS 
The material used in this investigation was taken from cats, 
dogs, rabbits, and white rats that were killed by illuminating 
gas, and the tissue fixed immediately or at different intervals 
