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GLOSSARY. 



The branch, of natural philosophy 

 which treats of the nature and pro- 

 perties of light, the theory of colours, 

 the changes produced on light by 

 the substances with which it comes 

 into contact, and the structure of 

 the eye and of instruments for aid- 

 ing vision. 



Optom'eter. See Opsiom'eter. 



Oral (Lat. os, the mouth). Belong- 

 ing to or uttered by the mouth. 



Orbic'ular (Lat. orbic'ulus, a small 

 round ball, from orbis, a round 

 thing). Circular ; in anatomy, 

 applied to the muscles which sur- 

 round and close the eyelids and 

 mouth. 



Orbit (Lat. orbis, a wheel). In as- 

 tronomy, the curved course in 

 which any body, as the moon or a 

 planet, moves in its revolution 

 round a central body ; in anatomy, 

 the cavity or socket in which the 

 eye is situated. 



OrTbital (Orbit). Belonging to the 

 orbit. 



Or'bito-sphenoid. A term applied to 

 the lesser wing of the sphenoid bone, 

 which forms part of the orbit. 



Order (Lat. ordo). A group of genera, 

 agreeing in more general characters, 

 but differing in special conformation. 



Or'dinate (Lat. ordo, order). In 

 conic sections, a straight line drawn 

 from a point in the abscissa to ter- 

 minate in the curve. 



Organ (Gr. bpyavov, or'ganon, an in- 

 strument, from epyo>, ergo, I work). 

 A natural instrument, by which 

 some process or function is carried 

 on. 



Organic (Grr. bpyavov, or'ganon, an 

 instrument). Consisting of or pos- 

 sessing organs ; relating to bodies 

 which have organs ; in geology, ap- 

 plied to the accumulations or addi- 

 tions made to the crust of the earth 

 in various places by the agency of 

 animals or vegetable matter, and 

 to the fossil remains of animals and 

 vegetables ; in medicine, applied to 

 diseases in which the structure of 

 an organ is evidently altered. 



Or'ganism (Gfr. bpyavov, or'ganon, an ' 

 instrument). The assemblage of , 



living forces or instruments consti- 

 tuting a body. 



Or'ganize (Gfr. bpyavov, or'ganon, an 

 instrument). To form with suitable 

 organs, so that the whole may work 

 together in a body. 



Organog'eny (Gr bpyavo v, or'ganon, 

 an instrument ; yevvaco, genna'o, 

 I produce). The development of 

 organs. 



Organog'raphy (Gr. bpyavov, or'ga- 

 non, an instrument ; ypatyw, 

 graph'ii, I write). A description 

 of organs ; used especially with 

 regard to plants. 



Organol'ogy (Gr. bpyavov, or'ganon, 

 an instrument ; Xoyos, logos, dis- 

 course). A description of organs, 

 especially of the animal body. 



Orien'tal (Lat. o'riens, the east, from 

 o'rior, I arise). Eastern : relating 

 to the east. 



Ornithich'nites (Gr. bpvis, ornis, a 

 bird ; Ix^os, ichnos, a footstep). 

 Fossil footprints of birds. 



Orni'tholites (Gr. bpvis, ornis, a bird ; 

 \iOos, lith'os, a stone). The fossil 

 remains of birds. 



Ornithol'ogist (Gr. bpvis, ornis, a 

 bird ; \oyos, logos, discourse). A 

 person who is skilled in the know- 

 ledge of birds. 



Ornithorogy (Gr. bpvis, ornis, a bird ; 

 \oyos, logos, discourse). The 

 branch of zoology which describes 

 birds. 



Orol'ogy (Gr. bpos, or'os, a mountain ; 

 \oyos, logos, discourse). The science 

 which describes mountains. 



Or'rery. A machine to represent the 

 motions and aspects of the planets 

 in their orbits. 



Ortho- (Gr. bpQos, orthos, staight). A 

 prefix in compound words, signify- 

 ing straight. 



Orthocer'atite (Gr. bpQos, orthos, 

 straight; icepas, ker'as, a horn). 

 A genus of straight horn-shaped 

 fossil shells, with several chambers. 



Orthodrom'ics (Gr. bpQos, orthos, 

 straight ; Spo/uos, drom'os, a course). 

 The art of sailing in the arc of a 

 great circle, being the shortest dis- 

 tance between two points on the 

 surface of the globe. 



