84 - CHRISTIANNA SMITH 
From these observations of the lipoid content of the kidney 
of the cat, it can be seen that there is a characteristic distribution 
of the lipoid granules which varies under different conditions, 
the normal and pathological not appearing the same. Because 
of the abundant supply of lipoids, their characteristic formations, 
such as the granular forms of the rods of the ascending limbs, 
and distribution in the cat’s kidney, it should be a favorable 
place in which to study the relation of lipoids to mitochondria. 
The lipoid content of the cat’s kidney may be summarized as 
on page 85. 
The results obtained from the study of the kidneys of other 
animals are added here with the realization of their incomplete- 
ness and the need of further study. E. T. Bell summarizes the 
factors which have caused confusion in the study of fat in muscle 
fibers (12). They might well be repeated here in regard to the 
lipoid content of the kidney. They are the following: 1) the 
character of the fat stain employed; 2) the species of animal; 
3) the character of the animal’s food; 4) the general nutritive 
condition of the animal; 5) the effect of fixatives; 6) the effect of 
postmortem changes. That the character of the fat stain and 
fixatives employed and conditions of the animal are very im- 
portant is easily seen from the study of the lipoid content of the 
cat’s kidney. That the species of the animal and effect of post- 
mortem changes must also be considered is evident from the 
following observations on the dog, rat, and rabbit. 
Dog 
Although it might be expected that the dog and cat would 
have kidneys very similar in their lipoid content, the reverse 
was found to be true. Of the six dogs examined, none presented 
the rayed appearance of the cortex so characteristic of the 
kittens and. half-grown cats, but looked more nearly like the 
very fat kitten (fig. 3). T'wo of these six dogs were five-day-old 
puppies, one a puppy not yet weaned, but whose exact age was 
not known, two were two weeks and five days old, and one a 
half-grown dog with the mange. On the kidney of the puppy 
of unknown age the following observations were made. 
