HYDANTOIN 



173 



HYDRIDES 



Hydantoin, (hi-dan-to'in)=C 3 H4N20 2 : a crys- 

 talline substance; also called Glycolyl-urea, 

 obtained from uric acid. 



Hydatid, (hi'da-tid). [Gk. hydatis, vesicle.] 

 Bladder worm : the cystic form of the 

 larva in tape worms. 



Hydnei, (hid'ne-i). [Gk. hydnon, truffle.] = 

 Spine-bearing fungi: belonging to Hyrueno- 

 mycetes; having the hymenium spread over 

 the surface of spines, &c. 



Hydnocarpus, (hid-no-kar'pos). [Gk. hydnon, 

 tuber: karpos, fruit.] A plant belonging to 

 Flacourtiacese. H. inebrians = An Indian 

 tree: fruit used to poison fish. 



Hydnoreae, (hid'nor-e-e)=Cytinaceae, q.v. 



Hydnum, (hid'num). [Gk. hydnon, truffle.] 

 A fungus. H. repandrum=.T3.edge}iog mush- 

 room. 



Hydra, (hi'dra). [L. hydra, water serpent.]= 

 1. The Snake: also called Serpens Aquations, 

 a widely extending constellation in the 

 southern heavens: the chief star of which is 

 Alphard. 2. Fresh- water polyp; the type of 

 Hydrozoa ; about J inch long, with long 

 slender tentacles, reproduced by buds, which 

 soon drop off. A perfect hydra grows from 

 any fragment. H. tubes= Generative system 

 of some hydrozoa: a trumpet-shaped body, 

 with mouth and tentacles, which breaks up 

 into Ephyrse, which, in turn, reproduce 

 hydra tubes=The second stage of Rhizos- 

 tomidscr=Trophosome of R.=Fixed R. 



Hydra- (hi'dra). [Gk. hydor, water.] A pre- 

 fix, implying water or hydrogen as a con- 

 stituent. 



Hydra sounding machine: used in the Porcu- 

 pine expedition of 1869, named from being 

 first used in the ship Hydra. 



Hydrachnidae, (hi-drak'ni-de). [Hydra and 

 Arachnida,g.i;.]= Water mites: small animals, 

 belonging to Acarina; parasitic on aquatic 

 insects. 



Hydracids, (hi-dras'idz). [Hydra and Acid.] 

 Acids in which hydrogen is an essential 

 element, as hydrochloric acid; mostly gaseous. 

 Formerly used when oxygen was regarded 

 as the more usual constituent of acids. Now 

 all acids are regarded as hydracids. 



Hydradephaga, (hi-dra-defa-ga). [Hydra, q.v.; 

 Gk. phago, I devour.] Predacious aquatic 

 beetles, belonging to Coleoptera. 



Hydras, (hi'dre). [Hydra, q.v.] = Plural of 

 Hydra: a sub-division of Hydrozoa, said to 

 be named from the fact that a perfect animal 

 will grow from any portion of one. 



Hydrales, (hi-dralez). [Hydra, q.v.] Aquatic 



Slants, with unisexual flowers, forming a 

 ivision of Endogens. 



Hydramides, (hi'dra-midz). [Hydra and 



Amide, q.v.] Ammonia and aromatic acids. 



Hydramyle, (hi'dra-mil). [Hydra and Amyl, 



.i;.]=C5Hio=Hydride of Amyl: a fluid, the 



vapour of which is an anaesthetic. 



Hydrangea, (hi-dran'ge-a). [Gk. hydor, water; 



aggos, vessel.] A plant, the type of Hydran- 



igeaceae, (hi-dran-je-a'se-e). [Hydran- 

 gea, q.v.] = Hydrangeads : shrubs, with 

 opposite leaves and large flowers, belonging 



to Saxifragales. Named from growing in 

 moist places. 



Hydrargo, (hi-drar'go). [Hydrargyrum.] A 

 prefix implying the presence of mercury. 



Hydrargyrum, (hi-drar'ji-rum). [Gk. hydor, 

 liquid; argyron, silver.] Hg" = Mercury: a 

 metallic element, liquid between 660 and 

 38 F. ; lustrous, and not readily oxidisable; 

 much used in the arts. 



Hydrate, (hi'drat). [Gk. hydor, water.] H. 

 of ammonium Ammonia. H. of carbon: 

 compounds containing carbon with hydrogen 

 and oxygen in the proportions contained in 

 water. H. of i)'on=Limonite = Prismatic 

 iron-ore = Brown oxide of iron. H. ofpotas- 

 iur;i=Caustic potash. 



Hydrated, (hi-dra'ted). [Hydrate, q.v.] Com- 

 bined with water so as to form a hydrate. 



Hydrates, (hi'drats). [Hydra, q.v.] Com- 

 binations of substances with water, in 

 definite proportions and with great affinity. 



Hydraulic, ( hl-draw'lik ). H. pressure: the 

 pressure of water ; capable of being applied 

 with great force and delicate manipulation. 

 H. press: an apparatus for the application of 

 great power by 

 means of water ; 

 also called Bramah 

 press. H. hme: har- 

 dens under water. 

 H. ram ; a ram 

 acted upon by hy- 

 draulic pressure. 

 H. tourniquet: an 

 instrument for cau- 

 sing the rotation of 

 a tube, having bent 

 ends, from which 

 water is allowed to 

 flow ; also called 

 Barker's mill, q.v. Hydraulic press. 



Hydraulics, (hi-draw'liks). The application 

 of the laws of hydrostatics to the use of water 

 as a motive power, or to the raising of 

 water. 



Hydric, (hi'drik). [Hydrogen, q.v.] A gene- 

 ral prefix for salts, in which hydrogen acts 

 as a metal, v. Hydrogen. H. bromate= 

 Bromic acid=HBrO 3 . H. bromide=Hydro~ 

 bromic acid=HBr. H. chlorate=Ch\oric 

 acid=HC!O 3 . H. cMon'de=Hydrochloric 

 acid=HCL H, cyanide=Hydrocyanic acid 

 =HCy. H. dioxide=H.ydroxyl=H 2 O<2. H. 

 ./h(oride=Hydrofluoric acid=HF. U. iodate 

 =Iodic acid=HIO 3 . H. iodide=HydriodiG 

 acid=HI. H. mtrate=Nitric acid=HNO 3 . 

 H. perbromc.te = Perbromic acid = HBiO,i. 

 H. perchlorate Perchloric acid = HCKV 

 H. peroxide=HydroxyI= HoC^. 



Hydrida, (hi'dri-da). [Hydra, q.v. ; Gk. eidos, 

 form. ]=Gymnochroa Hydra, q.v. 



Hydride, (hi'dri-de). [Hydras, q.v. ; Gk. eidos, 

 form.] A family of venomous sea-snakes. 

 v. Ophidia. 



Hydrides, (hi'dridz). [Hydra, q.v.] Com- 

 pounds of hydrogen with another element. 

 I/, of eaproyl=Hexyl. H. of hydrogen= 

 H 2 =Di-hydrogen. H. of cenanthyl=Heptyl. 

 JL. of methyl Marsh gas; causes death by 



