PRODUCTION AND CONSERVATION OF FATS AND> OILS. 39 
cent of the aggregate of the oils and fats which we imported from 
foreign countries in 1914. In 1917 they formed only 3 per cent, due 
not to any falling off in fish oil imports, but to greatly increased 
imports of soy bean and coconut oils. A number of varieties of 
fish are used for oil, and many more yield a small quantity of oil as 
a by-product from plants where they are canned or dried. Strictly 
speaking, sperm and other whale oils, as well as the dolphin and 
porpoise oils, do not belong in the same class with menhaden and the 
related drying fish oils. The production, importation, and exporta- 
tion of these oils are shown in Tables 2,4,5, and 7. Straight fish oil 
and fish liver oil are reported together as there is only a very small 
amount of pure liver oil made in this country. Recently a refining 
process in which hydrogen instead of steam is used to blow the oil 
has been developed. It appears that it is now possible to remove 
the disagreeable odor and flavor from some kinds of fish oils and 
render them suitable for food. For several years whale and possibly 
some fish oils have been hardened by hydrogenation in Norway and 
Germany, and within the last six months a lard substitute made in 
this way from Pacific coast herring oil has appeared on the American 
market. At present, however, fish oils are classed as technical oils, 
and are used chiefly in the manufacture of leather dressings, soap, 
and, to some extent, in making cheap paints. 
HOW TO INCREASE THE SUPPLY. 
The older methods for obtaining fish oils, which fortunately are 
now falling into disuse, consisted merely in permitting fish and scrap 
to rot, or, at best, in cooking the partly decomposed material in open 
kettles and skimming off the oil as it rose to the top. If care is taken 
to render with steam the fish before they have begun to decay and 
to press the fish scrap and residue from the rendering tanks, larger 
yields of a greatly superior oil are possible. There is no well- 
established market for fish oils other than the menhaden, herring, 
cod and cod liver oils, and comparatively few of the fish packers are 
equipped to make a good grade of oil. The fishermen, therefore, 
throw away much of their catch which is not suitable for food pur- 
poses, and a great deal of the refuse from the canneries is used only 
as fertilizer, or dumped back into the water. Many firms are coming 
to realize that it is perfectly possible to create a good market for 
fish meal as a stock feed, and that it will be profitable for them to 
press their refuse material to obtain the oil and grind the pressed 
cake for feed. 
This country uses, and produces in small quantities, a great many 
special oils from such marine animals as the whale, the porpoise, 
and the seal. Nearly all of these are manufactured to supply some 
