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JELLY ACIDS OILS. 169 



Vegetable jelly, or the pectinaceous alimentary principle in vegeta- 

 bles has starch for its basis ; with pectine, or pectic acid. These last 

 are veaeto-gelalinous substances. They are extensively distributed 

 in the various pulpy fruits, as we shall notice in another volume, to 

 which the reader is referred for useful and interesting particulars on 

 this subject. This principle is also found in the carrot, turnip, celery, 

 Jerusalem artichoke, onion, beet, and other roots. Pectine and its 

 acid are analogous, but the first dissolves in cold water, while the acid 

 is not easi'y soluble. ISu^ar dissolved in a solution of pectine, forms a 

 partial jelly, which is manifest in the preparation of fruits. It is con- 

 sidered nutritive and easily digestible; perhaps not unlike gum. It is 

 composed of caibon and water, and is considered an element of res- 

 piration. 



An acidulous principle is also an element of food. Succulent herbs, 

 as well as fruits, contain vegetable acid. Vinegar has been employ- 

 ed in all ages as an aliment, or rather the substances containing it, 

 and veritable acids are considered necessary for the preservation of 

 health, but they undergo no chemical change in the body, except to 

 combine with a base. Scurvy is a common result of abstinence from 

 succulent vegetable substances having the organic acids; and the ben- 

 eficial effects of these acids appear to be owing to the existence of a 

 salt with which they are capable of being incorporated in the system. 

 No artificial preparation of these equals the natural fruit or vegetable 

 substance. All vegetable acids are not, however, equally valuable as 

 a constituent of food. They are, as we have before mentioned, highly 

 grateful and cooling ingredients in drinks. But further particulars 

 respecting vegetable acids will be given under the head of fruits, par- 

 ticularly vinegar, or acetic acid, which, as we have seen, is of much 

 importance with solids and other articles of food. Vinegar in a pure 

 state cannot be strictly considered an alimentary principle. The com- 

 mon vinegar may be so considered, from the fact that it contains a 

 portion of starch, sugar, gum and gluten, but it is less necessary in 

 cold climates than in warm ones. 



The alcoholic principle we have before alluded to. It should not be 

 considered an alimentary principle. Alcohol has also been detected 

 in the blood, the brain, the urine and the bile. 



Oleaginous aliments are the fixed and volatile oils of vegetables ; 

 and these, it will have been seen, are before spoken of under the 

 heads of the plants affording them. The fixed vegetable oils affix a 

 permanent greasy stain to paper, while the volatile may be removed 

 by a moderate heat. In the vegetable kingdom, oils are obtained 



chiefly from seeds, such as rape, poppy, mustard jeeds, and nutmeg, / 



also from various roots, described in the next volume. The proportion 

 of this in black mustard is 18, linseed 22, and maize 11 to 18. 



The fixed oils are composed of several fatty or saponaceous princi- 

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