hydrencephalus 
hydrencephalus (hi-dren-sef'a-lus), . [NL., 
< Gr. v6up (Mp-), water, + eynci/iaAof, brain : see 
rncephalon.] Same as hydrocephalus, 1. 
hydrenterocele (hl-dren'ter-o-sel), n. [< Gr. 
i'<Wp (Mp-), water, + evrepov, intestine, + ////, 
tumor.] Intestinal hernia tlie sac of which in- 
closes water. 
hydria (hi'dri-a), .; pi. hydriiK (-e). [L.,<Gr. 
vSpia, a water-pot, < voup (in" 
dro-.] In <tr- 
cltwol., a large 
Greek vase, 
used especially 
f or carrying wa- 
ter. It has a capa- 
cious body, with a 
narrow mouth and 
usually a broad rim, 
and three handles, 
one at the back ex- 
tending above the 
rim, and a smaller 
one on each side. 
hydriad (M'dri- 
ad), n. [< Gr. 
Mpias (iiopiafi-), 
of the water 
2934 
sea by the pressure of the superincumbent 
water. 
Hydrobata (hi-drob'a-ta), n. [NL., < Gr. Map 
, water, + /MrWtOne that treads, < flaivetv, 
A genus of birds, the dippers, giving 
water-nymphs), 
< Mop (vop-), wa- 
ter.] In myth., Hydria, in the Museum of Fine Arts, 
a water-nymph. Boston, Massachusetts. 
hydriae (hi'dri- 
e), n.pl. [L.] 1. Plural of hydria. 2. [cap.] 
[NL.J Agroupof lepidopterous insects. Hiib- 
ner, 1816. 
hydric (hi'drik), a. [< hi/dr(ogen) + -ic.] Per- 
taining to, combined with, or containing hydro- 
gen. 
hydrid 1 , hydride (hi'drid, -drid or -drid), . [< 
hydr(ogen) + -id 1 , -ide 1 .] In cheni., a substance 
consisting of hydrogen combined with an ele- 
ment, or with some compound radical whicli 
plays the part of an element: as, phosphorus 
hydrid; amyl hydrid. 
hydrid 2 (hi'drid), . A fresh-water polyp of the 
family Hydrida>; a hydra. 
Hydridae (hi'dri-de), n.pl. [NL., < Hydra + 
-ida:] 1. A family of hydrozoans, typified by 
the fresh-water genus Hydra, alone represent- 
ing in some systems the suborder Eleuthero- 
blastea, of the order Hydroida. They are solitary 
polyps of simplest structure, maturing the sexual pro- 
ducts in the gastral wall, and also propagating asexually 
by budding or fission. The process of oudding is similar 
to that which takes place in colonial hydromedusans, only 
the buds become detached so that the polyp remains soli- 
tary; therefore Glaus and others consider the Hydridte 
simply as a family of Hydromedusie. See cut under Hy- 
drozoa. 
2. In Gray's classification, a group of serpents, 
containing the venomous sea-serpents or Hy- 
drophidce, with many harmless snakes belong- 
ing properly to several different families. 
hydride, n. See hydrid 1 . 
hydriform (hi'dri-form), a. [< NL. hydriformis, 
< hydra, q. v., + L. forma, shape.] Relating to 
or resembling a hydra, or one of the Hydroida ; 
hydroid. Also hydraform. 
hydriodate (hi'dri-o-dat), n. [< hydriod(ic) + 
-ate 1 .] A salt of hydriodic acid. 
hydriodic (hi-dri-od'ik), a. [< hydr(ogen) + 
iod(ine) + -ic.] Produced by the combination 
of hydrogen and iodine Hydriodic add. HI, a 
colorless gas formed by combining hydrogen and iodine, 
having a suffocating odor and fuming in the air. Its com- 
pounds with bases are called iodides. 
hydro-. [< L. hydro- (> It. idro- = Sp. hidro- = 
Pg. F. hydro-), < Gr. Mpo-, before a vowel Mp-, 
the usual combining form (Mar- being the usual 
derivative form) of Map (stem Mar-), water: 
see water.] An element in many compound 
words of Greek origin, meaning 'water.' In 
chemical compounds other than hydrogen it usu- 
ally represents hydrogen. 
hydroa (hi-dro'a), n. [NL., < Gr. Mop (Mp-), 
water, -r yov = L. ovum, egg.] In pathol., a 
name of certain forms of vesicular or bulbous 
eruptions, usually regarded as forms of pemphi- 
gus, also of forms of herpes and herpes iris, and 
of sudamina. 
hydroadenitis (hi-dr6-ad-e-ni'tis),K. [NL. 
(prop. *hydradenitis), < Gr. Mop (Mp-), water, 
+ NL. adenitis, q. v.] In pathol., inflammation 
of the sweat-glands. 
hydrpadipsia (hi"dro-a-dip'si-a), n. [NL., < 
Gr. Mop (Mp-), water, + NL. adipsia, q. v.] In 
pathol., a lack of thirst. 
hydrobarometer (hi' / dr6-ba-rom'e-ter), n. [< 
Gr. Map (Mp-), water, + E. barometer.] An 
instrument for determining the depth of the 
go, walk.] 
name to the family Hydrobatida; : a synonym of 
Cinclns. I'ieillot, 1816. 
Hydrobates (hi-drob'a-tez), n. [NL. : see Hy- 
Mp-), water: see hy- drobata.] 1. Same as Hydrobata. Boie, 1822. 
2. The typical genus of water-bugs of the 
family Hydrobatidie. Erichson, 1848. 
Hydrobatidae (hl-dro-bat'i-de), n.pl. [NL., < 
Hydrobata + -ida;.] 1. A family of turdoid 
passerine birds, the dippers or water-ouzels, 
named from the genus Hydrobata: a synonym 
of Cinclida!. See cuts under Cinclida; and dip- 
per. 2. A family of heteropterous insects, of 
elongate form, with the head sunken in the tho- 
rax up to the prominent rounded eyes, reflexed 
rostrum, 4-jointed antennae, and inconspicuous 
ocelli if any. They live on the surface of the 
water, and are collectively called water-striders. 
hydrobenzamide (hi-dro-ben'za-mid or -mid), 
w. [< hydro(gen) + benzamide.] A compound 
(C 2 iH 1 gN 2 ) obtained by the action of aqueous 
ammonia on bitter-almond oil. 
hydrobiosis (hi'dro-bi-p'sis), n. [< Gr. Mop 
(Mp-), water, + /fc'o?, life, + -o.w.J The de- 
velopment of living organisms, as bacteria, in 
fluid media; the conditions of life of such or- 
ganisms. 
hydrobiotite (h!-dro-bi'o-tlt), . [< Gr. Mop 
(Mp-), water, + biotitc.] A hydrated biotite, 
related to the vermiculites. 
Hydrobius (hi-dro'bi-us), n. [NL. (Leach. 
1817), < Gr. Mop (Mp-), water, + fitof, life.] 
A genus of water-beetles of 
the family Hydrophilida;, 
having 9-jointed antennas 
and slender palpi, with well- 
compressed and ciliated 
hind tarsi. It is a large and 
very wide-spread group, 
including 16 North Ameri- 
can species. 
hydroboracite (hi-dro-bo'- 
ra-sit), n. [< Gr. Map (Mp-), 
water, + borax (-ac-) + 
-ite 2 .] A mineral of white 
color, resembling fibrous ^ *** natural size.) 
and foliated gypsum. It is hydrated calcium 
and magnesium borate. 
hydrobranch (hi'dro-brangk), n. One of the 
Hydrobranchiata. 
Hydrobranchia (hl-dro-brang'ki-a), n.pl. Same 
as Hydrobranchiata. 
Hydrobranchiata (hl-dro-brang-ki-a'ta), n. pi 
[NL.,<Gr. Mop(Mp-), water,+ fipayxia, gills, + 
-ata.] In Lamarck's latest classification, a di- 
vision of gastropods, distinguished from Pneu- 
inobranchiata, and containing species which 
breathe water only. The section imperfectly 
corresponds to the nudibranchiates, infero- 
branchiates, and tectibranchiates of Cuvier. 
hydrobranchiate (hi-dro-brang'ki-at), a. Per- 
taining to or having the characters of the Hy- 
drobranchiata. 
hydrobromate (hi-dro-bro'mat), . [< hydro- 
bromic + -ate 1 .] A salt of hydrobromic acid: 
same as bromide. Also called bromhydrate. 
hydrobromic (hi-dro-bro'mik), a. [< hydro(gen) 
+ brom(ine) + -ic'.] Composed of hydrogen 
and bromine Hydrobromic add, HB, an acid pre- 
pared by bringing phosphorus and bromine together with 
a little water. It is a colorless gas, having a strong suffo- 
cating odor, fuming in the air, and very soluble in water. 
Its salts are called bromides. The acid is somewhat used 
in medicine as a substitute for the bromides. 
Hydrocampa (hi-dro-kam'pa), . [NL. (La- 
treille, 1825), < Gr. Mop (Mp-), wa 
, water, + 
caterpillar. ] The typical genus of moths of the 
Hydrocampa fenuinalts. (About twice natural size. ) 
family Hydrocampidce, havingconspicuous max- 
illary palpi, distinct ocelli, and a short probos- 
cis. The larvae live hidden under floating leaves, and make 
hydrocephalus 
for themselves cases of two oval bits of leaf. The genus is 
widely distributed in most parts of the world, though the 
species are few and none are North American. H. HJ/WI- 
phasata and //. tstagnata. are two British species, known as 
rltitia-markx. Also Hydrocampe. 
Hydrocampidse (lii-dro-kam'pi-de), n.pl. [NL., 
< Hydrocaiiiiid -f -iVta'.J A family of pyralid 
moths, typified by the genus Hydrocampa : so 
called from the aquatic habits of the larva?. 
Hydrocanthari(hi-dro-kan'tha-ri),w.jj/. [NL., 
< Gr. v6up ( ldp-) 9 water, + navdapo*;, a beetle. ] In 
Latreille's system of entomological classifica- 
tion, the swimmers: the third tribe of pentamer- 
ous Coleoptera, including the aquatic carnivo- 
rous beetles, of the old genera Dytiscus and Gy- 
rinus. It thus includes the modern families Dytiscidtr 
and Gyrinidte, and is identical with the modern group //)/ 
dnulephaga. Also Hydrocanthartfa, llydrocantharidoe. 
hydrocarbide (hl-dro-kar'bid or -bid), n. Same 
as hydrocarbon. 
hydrocarbon (hi-dro-kar'bon), M. [< hydro(gen) 
T carbon.] A compound of hydrogen and car- 
bon ; the general name of any compound con- 
sisting of hydrogen and carbon alone. The hydro- 
carbons are an exceedingly large and important group of 
compounds, and with their derivatives form the subject- 
matter of organic chemistry. Hydrocarbon black, 
burner, engine, furnace, etc. See the nouns. 
hydrocarbonaceous (hi-dro-kar-bo-na'shius), 
a. [< hydrocarbon + -aceous.] Consisting of 
or having the nature of hydrocarbon. 
In order to obtain the highest illuminating power of a 
flame in which hydrocarbonaceoua compounds are under- 
going combustion, the regulation of the supply of air is 
essential. Lommel, Light (trans.), p. 5. 
hydrocarbonatet (hi-dro-kar'bo-nat), n. [< hy- 
drocarbon + -ate 1 .] Carbureted hydrogen gas. 
hydrocarbonic (Wdro-kar-bon'ik), a. [< hy- 
drocarbon + -ie.] Pertaining to or having the 
nature of hydrocarbon. 
hydrocarbonous (hi-dro-kar'bo-nus), a. [< hy- 
drocarbon + -ous.] Same as hydrocarbonic. 
This hydrocarbonous pyrocone is closely surrounded or 
enveloped by gyrating, strongly-heated atmospheric air. 
W. A. Ross, Blowpipe, p. 71. 
hydrocarburett (hi-dro-kar'bu-ret), n. [< hy- 
dro(gen) + carburet, q. v.] Carbureted hydro- 
gen gas. 
hydrocardia (hi-dro-kar'di-a), n. [NL., < Gr. 
vfop (iip-), water, H- KapAia = E. heart.] Same 
as hydropericardium. 
hydfocastorite (hi-dro-kas'tor-it), n. [< Gr. 
viup (vip-), water, + castorite": see castor 3 .] A 
hydrated silicate of aluminium and calcium, de- 
rived from the alteration of petalite from Elba. 
hydrocauli, n. Plural of hydrocaulus. 
hydrocauline (hi-dro-ka'lin), a. [< hydrocauhm 
T -jwe 1 .] Pertaining to or having the charac- 
ter of a hydrocaulus. 
hydrocaulus (hi-dro-ka'lus), . ; pi. hydrocaidi 
(-11). [NL., < Gr. ii'dup (Mp-), water, + mvMf, a 
stem.] In sool., the main stem of the co3nosarc 
of a hydrozoan. 
hydrocele (hi'dro-sel), n. [= F. hydrocele, < L. 
hydrocele,< Gr. vtSpuKf/Zr/, hydrocele, < iiAup (v6p-), 
water, + KJ/ZII, tumor.] In pathol., a collection 
of serous fluid in the cavity of the tunica vagi- 
nalis of the testis. Dunglison. 
hydro-cellulose (hi-dro-sel'u-los), n. See the 
extract. 
Cotton completely disorganised by acid, and obtained 
as a fine powder, seems to contain one molecule of water 
more than ordinary cellulose, and the substance thus pro- 
duced has been termed hydro-cellulose. 
Hammel, Dyeing of Textile Fabrics (1886X p. 7. 
hydrocephalic (hi"dro-se-farik or hi-dro-sef 'a- 
hk), a. [< hydroceplialAis + -ic.] Pertaining 
to or exhibiting hydrocephalus. 
hydrocephaloid (hi-dro-sef 'a-loid), a. [< hydro- 
ce]>halus + -aid.] Resembling hydrocephalus. 
Also hydrencephaloid. Hydrocephalold disease, a 
condition of somnolence or coma developed occasionally 
in children in conditions of exhaustion. It appears to 
depend on cerebral anemia. 
hydrocephalous (hi-dro-sef'a-lus), a. [< NL. 
hydrocephalus: see hydrocephalus.] Same as 
hydrocephaloid. 
hydrocephalus (hi-dro-sef'a-lus), n. [= F. hy- 
drocephale = Sp. hidrocefalo"=; Pg. hydrocephalo, 
< NL. hydrocephalus, < Gr. vdpoxefa'Aov, water in 
the head, < iioup (Mp-), water, + KtfyaKri, head.] 
1. In pathol., an accumulation of serous fluid 
within the cranial cavity, either in the subdural 
space (external hydrocephalus) or in the ven- 
tricles (internal hydrocephalus). Acute hydro- 
cephalus is usually, and apparently always, due to menin- 
gitis. (Seemeninyitiy.) Chronic hydrocephalus may be due 
to atrophy of the brain, to pressure on the veins of Galen 
by tumors or inflammatory products, or to other causes. 
Also hydrencephalua, hydrocranium. 
2. [cop.] In sool, a genus of trilobites. Bar- 
rande, 1846. 
