USED IN NATURAL HISTORY. 



63 



EXCORIA'TIOX. Ir. lat. ex, from; eo- 

 rium, skin. An abrasion, mark of 

 a part having been rubbed from 

 the surface. 



EXCO'RTICA. Lat. Without bark. 



EXCRE'TION. ) fr. lat. excer'nere, to 



EXC-RE'TORY. separate from. The 

 throwing off" those matters which 

 are supposed to be useless, or in- 

 jurious to organic life, as the per- 

 spiration in animals. An excre- 

 tion is a secretion thrown off. An 

 excretory vessel, or duct, is one 

 which transmits the fluid, secret- 

 ed by a gland, either externally, 

 or into the reservoirs, in which it 

 has to be deposited. Excretory 

 organ means any organ charged 

 with the office of excreting : thus, 

 the skin is said to be an excretory 

 organ, because through it the per- 

 spiration or sweat is excreted. 



EXCU'BITOR. Lat. One that watch- 

 es by night. . A sentinel. 



EXCU'RRENT. fr. lat. excurro, to run 

 out. A mode of ramification in 

 plants in which the axis remains 

 always in the centre, all the other 

 parts being regularly disposed 

 around it. Projecting beyond the 

 edge or point of anything. 



EXHALA'TION. fr. lat. exkalare, to 

 throw out, to exhale. That which 

 exhales from any body. A func- 

 tion, by the virtue of which cer- 

 tain fluids obtained from the blood 

 are spread, in the form of dew, 

 on the surface of membranes, ei- 

 ther for the sake of being thrown 

 out of the body, or to serve for 

 certain purposes. The sweat is 

 an example of an exhalation as 

 well as of an excretion. 



Exo. Gr. A prefix signifying with- 

 out, on the outside. 



Ex OCETUS. Lat. Generic name of 

 a kind of flying-fish. 



EXOCH'SATA fr. gr. exochos, promi- 

 nent. A designation of the long- 

 tailed Crustacea. 



EXO'GKNOUS. fr. gr. geinomai, to be 

 produced. Outside-growing} in- 



creasing in diameter by deposi 

 tion on the exterior. fr>. 22, Book 

 vii). 



EX'OOESTS. Exogenous plants. 



EXO'GTHA. fr. gr. exo, without; gt*- 

 ros, circle. Not circular. (Figs. 

 109, 115, 125, 135. Book viii). A 

 genus of unimuscular bivalves, 

 allied to the oyster. 



EXO'LETE. Worn or faded. Appli- 

 ed to shells. 



EXO'SMOSE. fr. gr. exo, outside ; 6s 

 mos, impulsion. The property by 

 which a rarer fluid passes through 

 membranous substances, out of a 

 cavity, into a vessel containing a 

 denser fluid. 



EXO'TIC. fr. gr. exotikos, foreign. 

 Anything introduced into one 

 country, from some other country, 

 is so termed. 



EXPERIMENTUM cRccis. Lat. Cru- 

 cial experiment. A decisive expe- 

 riment, so called because, like a 

 cross or direction-post, it directs 

 men to true knowledge. 



EXPLO'SIOX. A sudden bursting, 

 with noise and violence. 



EXSE'RTED. fr. lat. excertus, thrust 

 out. Applied to the stamens of 

 plants when they are longer than 

 the corolla. 



EX'SICCATED. Dried up. 



EXSTI'PULATE. Without stipules. 



EXTEND. To straighten ; to stretch 

 out. When a limb is straightened 

 it is said to be extended. 



EXTEX siLE.-fr. lat. extendo, I stretch. 

 Susceptible of being extended or 

 lengthened. Having the power 

 to extend itself. 



EXTEN'SORS fr. lat. extenders, to 

 stretch out. The muscles whose 

 office it is to extend certain. parts. 



EXTERNAL. Outside. It is used in 

 relation to the middle line of the 

 body; for example, the little toe 

 is external, and the big toe inter- 

 nal ; the corner of the eye next 

 to the nose, is the internal corner 

 and the other the external corner 

 of the eye. 



