(33) 



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 



