EXO 



EXT 



lalifolius. A perennial plant of the 

 vetch kind, which grows naturally in 

 some places ; is easily cultivated, and 

 annually yields a great burden of ex- 

 cellent provender, and might be cul- 

 tivated to advantage as a green food 

 for cattle on any of the more strong 

 sorts of soil. 



EXACERBATION. An increase 

 of violence in the symptoms of fe- 

 vers. 



EXCORIATION. A bruise or 

 abrasion of the skin : protection from 

 air by a linen rag, and mild oil lina- 

 ments are most serviceable. 



EXCRESCENCE. Any unnatu- 

 ral growth or tumour. 



EXCRETION. In physiology, the 

 separation of useless or injurious por- 

 tions of matter from the system, as 

 urine, expired air, feces, perspiration. 

 The excretions of plants have called 

 forth much discussion. De Candolle 

 imagined that the inability of plants 

 to grow for a long time on the same 

 spot was due to the deposite of ex- 

 cretions. Mr. Gyde has examined 

 this matter thoroughly, and shown 

 that the excretions are not injurious ; 

 the amount is very small, and iden- 

 tical in composition with the sap ; 

 he also found that a plant might be 

 watered with a solution of its excre- 

 ment with great benefit. 



EXFOLIATION. The separation 

 of diseased bone from that which is 

 sound in the progress of a disease. 



EXHALATION. Evaporation at 

 ordinary temperatures, more espe- 

 cially from a living or solid surface. 



EXHAUSTION. In physics, the 

 removal of air or gases from the in- 

 terior of bodies. 



EXOGENOUS (from ef, outside, and 

 ■yeivofiai, I grow). A term applied to 

 those plants a transverse slice of 

 whose stem exhibits a central cellular 

 substance or pith, an external cellular 

 and fibrous ring or bark, and an inter- 

 mediate woody mass, and certain fine 

 lines radiating from the pitli to the 

 bark through the wood, and called 

 medullary rays. They are called ex- 

 ogens, because they add to their 

 wood by successive external addi- 

 tions, and are the same as what are 

 864 



otherwise called dicotyledons. They 

 constitute one of the primary classes 

 into which the vegetable world is di- 

 vided, characterized by their leaves 

 being reticulated ; their stems having 

 a distinct deposition of bark, wood, 

 and pith ; their embryo with two co- 

 tyledons ; and by their flowers usu- 

 ally formed on a quinary type. Our 

 forest-trees and most garden vegeta- 

 bles are of this kind. 



EXORRHIZ-E (from e^, and p^'a, 

 a root). Exogenous or dicotyledon- 

 ous plants, the roots of which extend 

 directly from the embryo. 



EXOSMOSE (from tf, and uafioc, 

 impulsion). The passage outward of 

 fluids, &c., the reverse oi Endosmosc, 

 which see. 



EXOSTOSIS (from e^, and ocrreov, 

 a bone). A tumour on a bone. In bota- 

 ny, any knot or tumour on a trunk or 

 large root : the wood is often finely 

 curled. 



EXOTICS. Foreign plants. 



EXPANSION. The increase in 

 dimensions produced by heat. In 

 the arts, it is a serious drawback on 

 perfect workmanship, for beams, me- 

 tallic tires, &c., by the constant expan- 

 sions from heat, and contraction by 

 cold, are always acting upon masses 

 of masonry injuriously. Gases ex- 

 pand most rapidly and extensively, 

 fluids next, and metals least. 



EXPECTORANTS, Medicines 

 which assist in throwing off the 

 phlegm of the throat, as ipecacuan- 

 ha, tartar emetic, horehound, squills. 

 They are useful in dry coughs. 



EXPRESSED OILS. Such as are 

 obtained by pressure, as olive, lin- 

 seed, rape, castor, almond, as distin- 

 guished from volatile or essential oils. 



EXTRACT. The solid remaining 

 after boiling down an infusion or de- 

 coction to dryness. The heat used 

 should be from steam. The term 

 extractive is applied to that portion 

 which is of a brown colour, soluble 

 in water, and forms a colouring mat- 

 ter with alum solution. 



EXTRAVASATION. In surgery, 

 whenever blood or other fluids are 

 thrown out from the veins into the 

 skin, brain, or other parts, it is term- 



