252 TRANSACTIONS OF THE 
rich in A. Whale oil contains it to a somewhat less ex- 
tent as do fish oils generally. It is present, though by no 
means abundantly, in oleo oils and would therefore occur 
in oleomargarines made from these oils. This substitute 
cannot, however, be looked upon as being even in the 
same class with good butter as a source of this important 
factor. Nut margarines, on the other hand, made entirely 
from vegetable oils have been shown to be practically 
devoid of the fat-soluble growth promoting substance. 
It is present in egg yolk and in much less amounts in beef 
fat and in certain seeds, especially those carrying an abun- 
dance of yellow pigment. It is even present in yellow 
corn and absent in white. 
It has been shown to be present in the oil from pig’s 
liver, the liver and kidney tissue, and is thought by some 
to be present in all glandular tissue. Muscular tissue that 
we eat so abundantly, however, seems to carry this factor 
to a very slight extent. Lard lacks fat-soluble A, as does 
cottonseed oil and most other vegetable oils, red 
beets, parsnips, potatoes, etc. 
Leafy vegetables and green plant tissue of many 
kinds such as spinach, alfalfa, clover, timothy have been 
shown to carry the A factor. Tomatoes carry it in con- 
siderable abundance, cabbage, carrots, and sweet potatoes 
to a less extent, and it seems to be present in peas and 
possibly bananas. Unsweetened evaporated milk and 
milk powders probably also contain it. 
Stability.—Fat-soluble A seems to be relatively stable 
to the ordinary processes to which food products are 
usually subjected. Drying and ordinary cooking may 
destroy it to some extent, though substances which are 
relatively rich in it originally are not rendered completely 
inert by these ordinary processes. It can be destroyed 
by heating to 100°C or above for one hour or longer. 
Lower temperatures for longer periods, especially if the 
substance is exposed to light and air, seem detrimental. 
In fact, the length of the treatment seems to be as impor- 
tant as its intensity. Most of the above generalizations 
come from experimentation with butter fat. 
In plant tissue this vitamine seems to be relatively 
stable and withstands ordinary heating and drying pro- 
