HYDRATE 



580 



HYDROBIOSIS 



Hydrate (hi' -drat) [vdup, water]. A compound of an 

 elementary atom, or of a radical, with the radical 

 hydroxy I H-O- or -O-H , as the hydrogen atom may 

 be positive or negative. Practically a hydrate is con- 

 sidered as a molecule of water with its basic atom of 

 hydrogen replaced by another electropositive atom, e.g. , 

 potassium hydrate, K-O-H, is derived from water, 

 H-O-H. 



Hydration [hi-dra' 'shun) [ydup, water]. The process 

 by which a body or substance becomes impregnated 

 or saturated with water. 



Hydrazin (hi-draz' '-in) [vdup, water ; azotum, nitro- 

 gen], H 4 N„. I. Diamid; a colorless, stable gas, 

 soluble in water, having a peculiar odor and a strong 

 alkaline reaction. Orthin is prepared from it. .See 

 Phenyl-hydrazin. 2. One of a class of bodies de- 

 rived from hydrazin by replacing one or more of its 

 hydrogen atoms by a compound radical. 



Hydrazones {hi f -draz-ons) [ydup, water ; azotum, 

 nitrogen] . Phenylhydrazones ; a group of chemic 

 bodies produced by the action of phenylhydrazin 

 upon carbonyl compounds. They are usually crystal- 

 line compounds, insoluble in water. They are yellow 

 or brown in color, and almost invariably decompose 

 upon fusion. 



Hydrecium {Jii-dre' -se-urri) [ydup, water ; okoc, house : 

 pi. , Hydrecia~\. In biology, the sac for the reception 

 of the retracted cenosarc attached to the swimming- 

 bell of certain hydrozoans. 



Hydrectasis [hi-drek' '-tas-is) [vdup, water; f/craovc, 

 a stretching out]. Distention by water or by a watery 

 fluid. 



Hydremesis [hi-drem 1 '-es-is) [ydup, water ; efieoiq, 

 vomiting]. The vomiting of a watery material. 



Hydremia (hi-dre' '-me-ah) [vdup, water; alfia, blood]. 

 A watery condition of the blood due to defective 

 renal secretion or to imperfect fibrination. It accom- 

 panies albuminuria and certain other exhausting dis- 

 eases. 



Hydrencephal {hi' ' -dren-sefal ) [vdup, water ; kyak- 

 0«/loc, brain]. A hydrocephalic brain. 



Hydrencephalitis {hi-dren-sef-al-i' '-tis) [vdup, water; 

 eynktyaXoc, brain ; mc, inflammation]. Inflammatory 

 hydrocephalus. 



Hydrencephalocele {hi-dren-sef'-al-o-sil) [vdup, wa- 

 ter; kyuetyaXog, brain ; nrjXr], hernia]. Encephalocele 

 in which the tumor is in part composed of a watery 

 fluid. H. palatina, a variety of hydrencephalocele 

 in which the dura mater, distended with serum, pro- 

 jects into the mouth, forming a tumor possibly as 

 large as a small apple. 



Hydrencephalus {hi-dren-sef '-al-us). See Hydro- 

 cephalus. 



Hydrenterocele {hi-dren-ter' '-o-sel) [vdup, water; 

 ivrepov, intestine; nr/'Kri, hernia]. Intestinal hernia, 

 the sac of which contains some extravasated fluid. 



Hydrenterorrhea {hi-dren-ter-or-e' -ah) [vdup, water; 

 ivrepov, intestine; poia, flow]. A watery diarrhea. 



Hydriasis {hi-dri'-as-is). See Hydro-therapeutics. 



Hydriatic {hi-dre-atf -ik) [vdup, water; iarmdc, heal- 

 ing]. Pertaining to the cure of disease with water. 



Hydriatric {hi-dre-af -rik) [ydup, water; larpSg, physi- 

 cian]. Relating to the treatment of disease with 

 water. 



Hydriatry {hi'-dre-at-re). See Hydro-therapeutics. 



Hydric (hi'-drik) [vdup, water]. Containing water. 



Hydrid {hi f -drid) [vdup, water]. A chemic compound 

 containing hydrogen united to an element. 



Hydriodic {hi-dre-od' -ik) [ydup, water ; ludijc, like a 

 violet]. Containing hydrogen and iodin. H. Acid, 

 HI, a heavy, colorless gas, with a suffocating odor and 

 an acid reaction. It freezes at — 55 C. The syrup of 



hydriodic acid contains I per cent, of absolute HI. 

 Dose, 3J-iv, well diluted. 



Hydro- [hi'-dro-) [vdup, water], A prefix signifying 

 water, or that water forms a structural part. See, 

 also, Hydrate. 



Hydroa {hi-dro'-ah) [vdup, water; uov, egg]. A 

 term including a group of vesicular and bullous skin- 

 affections presenting many points of affinity with vesi- 

 cating erythemata, herpes, and pemphigus. The group 

 includes the diseases described as Dermatitis herpeti- 

 formis, Pemphigus pruriginosus, Urticaria vesicans, 

 and Herpes gestationis, and is by no means uncommon. 

 Hydroa occurs in individuals of the neurotic tempera- 

 ment ; its course is chronic, but with a decided tendency 

 toward ultimate recovery. {Hydroa, as the name of a 

 skin-disease, is much confused in meaning with Hidroa, 

 q. v.) H. bullosa. See H. pruriginosum. H. 

 aestivale. See H. vacciniforme. H. febrile. See 

 Herpes facialis. H. gestationis, that of pregnancy. 

 H. herpetiforme. Also called Dermatitis he/peti- 

 formis : Herpes gestationis ; Herpes circinatus bullo- 

 sus ; Pemphigus circinatus. See Pe??iphigus prurigi- 

 nosus. H. pruriginosum. Hydroa bullosa; a very 

 rare form, attended at its development with intense 

 itching, and sometimes preceded by slight febrile 

 symptoms, followed by the formation of small bulla? 

 not exceeding the size of a split pea, and commencing 

 as vesicles, without any antecedent lesion. Slight 

 umbilication occurs, followed by desiccation, and the 

 formation of scales or crusts. Successive crops are 

 formed, the bullae being discrete or grouped irregu- 

 larly, but never in circles. H. puerorum. See H. 

 vacciniforme. H. vacciniforme. Hydroa cestivale ; 

 Hydroa puerorum ; Recurrent summer eruption ; a 

 recurring summer eruption of boyhood, usually with 

 vesicles that leave scars. The disease generally 

 begins in the first, second, or third year of life, and is 

 often preceded by articular symptoms. The eruption 

 develops chiefly on the uncovered parts, and is generally 

 preceded by burning or pain, fulness of the region at- 

 tacked, anorexia, and insomnia. Red spots appear, and 

 on these rounded vesicles develop, singly or in groups, 

 varying in size from that of a millet-seed to that of a 

 large pea. They may coalesce into an irregularly out- 

 lined flattish bulla. The redness remains as an areola. 

 These bullae dry up, rupture, or become umbilicated, 

 and form crusts which, on separating, leave slightly 

 depressed scars resembling those of smallpox. The 

 pathology is unknown. 



Hydroadipsia {hi-dro-ad-ip' '-se-ah) [ydup, water ; a, 

 priv. ; ditpa, thirst]. Absence of thirst, or of desire 

 for water. 



Hydrobenzamid {hi-dro-ben' '-zam-id) [vdup, water; 

 benzoin; amid~\, C 2l H 18 N.,. Azobenzoyl hydrid, a 

 crystalline compound, soluble in alcohol. 



Hydrobenzoin {hi-dro-ben-zo' -in) [vdup, water; ben- 

 zoin\ , C ]4 H u 2 . A compound prepared by the action 

 of sodium amalgam on benzoin. It dissolves with 

 difficulty in water, is readily soluble in alcohol, and 

 crystallizes in large, shining, rhombic plates, melting 

 at 134 C. 



Hydrobilirubin {hi-dro-bil-e-ru'-bin) [vdup, water; 

 bilis, bile; ruber, red], C^H^N^Cy A rose-red or 

 brown-red pigment formed by treating a solution ol 

 bilirubin or biliverdin in dilute alkali with sodium 

 amalgam. It is slightly soluble in water, easily so in 

 alcohol, ether, and chloroform. It is a coloring- 

 matter of feces, said to be identical with stercobilin, 

 and is sometimes found in urine. 



Hydrobiosis {hi-dro-bi-o' '-sis) [vdup, water; ftloc, lifej. 

 In biology, the origin and maintenance of life in fluid 

 media. 



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