GLOSSARY. 



139 



drawn between any two points on 

 it, will altogether lie on the sur- 

 face ; applied also to an imaginary 

 flat surface supposed to pass through 

 a body. 



Plane Geometry. The geometry of 

 plane or flat surfaces, in opposition 

 to that of solids. 



Plan'et (Gr. irKa.vaop.ai, plana'omai, 

 I wander). A globe revolving 

 round the sun in aji elliptic orbit ; 

 the name having been given by the 

 ancients to such bodies on account 

 of the apparent irregularity of their 

 motions. 



Plan'etary (Or. TTACII/TJTTJS, planetes, a 

 planet). Consisting of, or relating 

 to planets. 



Plan'etoid (Gr. ir\avriTT)s, planetes, 

 a planet ; e5os, eidos, shape). A 

 name given to the bodies found by 

 astronomers in the space between 

 Mars and Jupiter, where, on 

 mathematical reasoning, a planet 

 would be expected. 



Planim'etry (Lat. pla'nus, flat ; 

 /j.eTpov, met'ron, a measure). The 

 measuring of plane surfaces. 



Pla'no-con'cave (Lat. pla'nus, flat ; 

 con'cavus, hollowed out). Flat on 

 one side and concave on the other. 



Pla'no-con'ical (Lat. pla'nus, flat; 

 co'nus, a cone) . Flat on one side 

 and conical on the other. 



Pla'no-convex' (Lat. pla'nus, flat; 

 convex/ us, convex). Flat on one 

 side and convex on the other. 



Plantar (Lat. plan'ta, the sole of the 

 foot). Belonging to the sole. 



Plan'tigrade (Lat. plan'ta, the sole of 

 the foot; grad'ior, I step). Walk- 

 ing on the sole of the foot, as the 

 bear. 



Plas'ma (Or. TrAao-trco, plasso, I form). 

 The colourless part of the blood,- 

 being the material from which the 

 tissues ai'e nourished. 



Plas'tic (Gr. irKaavw, plasso, I form). 

 Capable of being moulded into a 

 form ; giving a definite form. 



Plas'tron. The floor, in tortoises and 

 turtles, of the bouy encasement of 

 which the carapace forms the upper 

 part. 



Plat'y- (Gr. irAu*, plat' us, flat). 



A prefix in compound words, signi- 

 fying flat. 



Platycoelion (Gr. TTAOTUS, plat'us, 

 flat ; KOI\OS, koi'los, hollow). A 

 term applied to some fossil croco- 

 dilian reptiles, in which one end >f 

 the body of a vertebra was flat 

 and the other concave. 



Platys'ma (Gr. irAarui/w, platu'no, I 

 widen). An expansion ; in anatomy, 

 a broad thin muscular expansion 

 lying under the skin at each side 

 of the neck. 



Plectogna'thous (Gr. irAeKw, pletto, 

 I connect ; yvaQos, gnatJios, the 

 jaw). Applied to an order of 

 fishes which have the upper jaw 

 firmly attached to the skull. 



Plei'ades (Gr. TrAew, plco, I sail). A 

 cluster of seven stars in the neck of 

 the constellation Taurus ; the rising 

 of which, to the Greeks, indicated 

 the time of safe navigation. 



Plei'ocene (Gr. irteicov, plei'dn, more ; 

 Kaivos, kai'nos, new). A term in 

 geology for the upper tertiary group, 

 containing more of recent than of 

 extinct species. 



Pleis'tocene (Gr. ir\ei<TTos, pleis'tos, 

 most ; Kaivos, kai'nos, new). A 

 term applied in geology to the 

 upper or post-tertiary group, im- 

 plying that the organic remains 

 almost entirely represent existing 

 species. 



Ple'onasm (Gr. ir\eovafa, pleona'zo, 

 I am more than enough). The use 

 of more words than are necessary to 

 express an idea. 



Pleonas'tic (Gr. TrAeovao>, pleona'zo, 

 I am more than enough). Belong- 

 ing to pleonasm ; redundant. 



Plesiomor'phisni (Gr. 7r\7j<nos, pie- 

 sios, near ; pop^i], morphe, form). 

 Close but not identical resem- 

 blance in form ; applied to certain 

 crystals. 



Plesiomor'phous (Gr.irA7j<nos, plesios, 

 near ; pop^T), morphe, form). 

 Nearly of the same form. 



Pleth'ora (Gr. TTA^W, pletho, I be- 

 come full). Fulness ; in medicine, 

 fulness of blood; a full habit of 

 body. 



Pletho'ric (Gr. irArM pletho, I be- 



