434 DISEASE IN WILD MAMMALS AND BIRDS 
agency of fats because fat could only remove calcium as 
insoluble soaps and these are not at all increased. This 
fact contradicts the idea of fat starvation as a cause of 
rickets. Howland and Kramer found that the blood in 
active rickets had a normal or slightly lowered calcium 
content, but a regularly reduced phosphorus content. 
The latter deficiency was extreme at times. They ascribe 
to this deficiency the failure of the bones to calcify. It 
can be readily understood that a decrease of phosphorus 
in the blood would render difficult the precipitation of 
calcium phosphate. 
Recently two series of studies, the first by Pappen- 
heimer, Zucher and McCann and the second by Shipley, 
McCollum, Park and Simonds have shown that rats fed 
on a diet low in calcium but mth a sufficient amount of 
fat-soluble \T.tamine and phosphorus develop a bone con- 
dition mth many fundamental resemblances to rickets. 
They were also able to produce the condition with an 
excess of calcium and deficiency of phosphorus. On the 
first diet, the condition differs from rickets in that the 
arrangement of the proliferating zone of cartilage cells 
is maintained and the evidence of bone resorption in the 
diaphyses is excessive. A diet deficient in both calcium 
and phosphorus leads to an atj'pical rickets. 
In the animals autopsied at this Garden rickets 
occurred very much more frequently in the flesh-eaters 
than in any of the other dietary groups. On closer 
analysis it was found that rickets in almost every case 
appeared in the carnivores which did not receive bones 
as a part of the food. Rickets occurred frequently in the 
omnivorous macaques which however did not show osteo- 
malacia, although they belong to the same dietary group 
as the Cebidee. The reason they did not suffer the latter 
disease while adult but had rachitic young is probably 
due to the fact that this monkey group, which breeds best 
in our Garden, receives in addition to the diet given to 
Cebidae one raw egg. This increased the calcium content 
