90 



HOW CROPS GROW. 



. 17. 



as minute, transparent globules in the cells, f. From 

 these seeds the oil may be completely extracted by ether, 

 benzine, or sulphide of carbon, 

 which dissolve all fats with readi- 

 ness, but scarcely affect the other 

 vegetable principles. 



Many plants yield small quan- 

 tities of .wax, which either gives a 

 glossy coat to their leaves, or 

 forms a bloom upon their fruit. 

 The lower leaves of the oat plant 

 at the time of blossom contain, in 

 the dry state, 10 per cent of fat 

 and wax, (Arendt). Scarcely two 

 of these oils, fats, or kinds of wax, are exactly alike in 

 their properties. They differ more or less in taste, odor, 

 and consistency, as well as in their chemical composition. 



EXP. 39 Place a handful of fine and fresh corn or oat meal which has 

 been dried for an hour or so at a heat not exceeding 212, in a bottle. 

 Pour on twice its bulk of ether, cork tightly, and agitate frequently for 

 half an hour. Drain off the liquid (filter, if need be) into a clean porce- 

 lain dish, and allow the ether to evaporate. A yellowish oil remains, 

 which, by gently warming for some time, loses the smell of ether and 

 becomes quite pure. 



The fatty oils must not be confounded with the ethereal, 

 essential, or volatile oils. The former do not evaporate 

 except at a high temperature, and when brought upon 

 paper leave a permanent " grease-spot." The latter readily 

 volatilize, leaving no trace of their presence. The former, 

 when pure, are without smell or taste. The latter usually 

 possess marked odors, which adapt many of them to use 

 as perfumes. 



In the animal body, fat (in some insects, wax,) is formed 

 or appropriated from the food, and accumulates in consid- 

 erable quantities. How to feed an animal so as to cause 

 the most rapid and economical fattening is one of the 

 most important questions of agricultural chemistry. 



