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human food. This oil is both nutritious and wholesome, 
and furnishes a clean vegetable substitute for butter and 
lard, especially for cooking purposes. The poorer grades 
are used for soap-making and other mechanical purposes. 
In the process of extracting the oil the hulls are removed 
from the seeds and the kernels are partly cooked, after 
which the oil is removed by pressure. The cake that re- 
mains is ground into cotton-seed meal. This still contains 
considerable fat and a large amount of other nutriment 
and is an important food for cattle. Fixed oils differ from 
volatile oils in not completely evaporating when exposed 
to the air. In many cases the by-products resulting during 
the manufacture of the various oils are of considerable 
commercial importance. Some of these by-products are 
shown in the cases with the oils. In this connection are 
shown some vegetable waxes. These occur as exudations 
upon the surfaces of plants, especially those of leaves and 
fruits. Wax imparts a bluish-white color or “bloom” 
to such a surface, as upon pumpkins and grapes. Such a 
surface is called “glaucous” by the botanist. Another 
excellent illustration is the white surface upon the fruits 
of the bay-berry or wax-myrtle. Wax is related to fat. 
It is insoluble in water and is obtained by melting in hot 
water and skimming it from the surface. It is largely 
used in candle-making and also in pharmaceutical prep- 
arations. 
Resins. Cases 57 and 62.—The cases devoted to resins 
contain on the one hand a large trunk of the long-leaf pine, 
in which has been cut a turpentine box, together with a 
series of specimens of turpentine and rosin, illustrative of 
the trade-classification of these products, and, on the other 
hand, a series of resins derived from other species of pine 
and related trees, and also those from trees representing 
the mulberry family, the mimosa family, the sumac family, 
and the myrrh family. An important substance derived 
from the turpentine of the long-leaf pine and other species 
of pine trees is pine tar or pix liquida. Pine tar may 
