Zygobranchia
Zyg•o•bran´chi•a, n. pl. [NL., from Gr. zygo•n a yoke + a gill.] (Zoöl.) A division of marine gastropods in which the gills are developed on both sides of the body and the renal organs are also paired. The abalone ( Haliotis) and the keyhole limpet ( Fissurella) are examples.

Zygobranchiate
Zyg•o•bran´chi•ate, a. (Zoöl.) Of or pertaining to the Zygobranchia. { Zyg•o•dac´tyl, Zyg•o•dac´tyle }, n. [See Zygodactylic.] (Zoöl.) Any zygodactylous bird.

Zygodactyli
Zyg•o•dac´ty•li, n. pl. [NL.] (Zoöl.) Same as Scansores. { Zyg•o•dac´ty•lic, Zyg•o•dac´tyl•ous ( 277), } a. [Gr. zygo•n a yoke, pair + finger, toe: cf. F. zygodactyle.] (Zoöl.) Yoke-footed; having the toes disposed in pairs; — applied to birds which have two toes before and two behind, as the parrot, cuckoo, woodpecker, etc.

Zygomatic
Zyg•o•mat´ic ( 277), a. [Cf. F. zygomatique.] (Anat.) Of, pertaining to, or in the region of, the zygoma. Zygomatic arch, the arch of bone beneath the orbit, formed in most mammals by the union of the malar, or jugal, with the zygomatic process of the temporal bone. In the lower vertebrates other bones may help to form it, and there may be two arches on each side of the skull, as in some reptiles. — Zygomatic process, a process of the temporal or squamosal bone helping to form the zygomatic arch. { Zyg•o•mor´phic, Zyg•o•mor´phous } a. [Gr. zygo•n a yoke + form.] (Biol.) Symmetrical bilaterally; — said of organisms, or parts of organisms, capable of division into two symmetrical halves only in a single plane.

Zygophyte
Zyg´o•phyte, n. [Gr. zygo•n a yoke + fyto•n a plant.] (Bot.) Any plant of a proposed class or grand division ( Zygophytes, Zygophyta, or Zygosporeae), in which reproduction consists in the union of two similar cells. Cf. Oöphyte.

Zygosphene
Zyg´o•sphene, n. [Gr. zygo•n a yoke + a wedge.] (Anat.) A median process on the front part of the neural arch of the vertebrae of most snakes and some lizards, which fits into a fossa, called the zygantrum, on the back part of the arch in front.

Zygospore
Zyg´o•spore, n. [Gr. zygo•n a yoke + E. spore.] (Bot.) (a) Same as Zygosperm. (b) A spore formed by the union of several zoöspores; — called also zygozoöspore.

Zymase
Zym´ase, n. [From Zyme.] (Physiol. Chem.) A soluble ferment, or enzyme. See Enzyme.

Zymic
Zym´ic, a. (Old Chem.) Pertaining to, or produced by, fermentation; — formerly, by confusion, used to designate lactic acid.

Zymogen
Zym´o•gen, n. [ Zyme + - gen.] (Physiol. Chem.) A mother substance, or antecedent, of an enzyme or chemical ferment; — applied to such substances as not being themselves actual ferments, may by internal changes give rise to a ferment.
"The pancreas contains but little ready-made ferment, though there is present in it a body, zymogen, which gives birth to the ferment." Foster.

Zymogene
Zym´o•gene, n. [ Zyme + root of Gr. to be born.] (Biol.) One of a physiological group of globular bacteria which produces fermentations of diverse nature; — distinguished from pathogene.

Zymogenic
Zym•o•gen´ic, a. (Biol.) (a) Pertaining to, or formed by, a zymogene. (b) Capable of producing a definite zymogen or ferment. Zymogenic organism (Biol.), a microörganism, such as the yeast plant of the Bacterium lactis, which sets up certain fermentative processes by which definite chemical products are formed; — distinguished from a pathogenic organism. Cf. Micrococcus. { Zy•mo•log´ic, Zy•mo•log´ic•al } a. [Cf. F. zymologique.] Of or pertaining to zymology.

Zymology
Zy•mol´o•gy, n. [ Zyme + - logy: cf. F. zymologie.] A treatise on the fermentation of liquors, or the doctrine of fermentation. [Written also zumology.]

Zymolysis
Zy•mol´y•sis, n. [NL. See Zyme, and Lysis.] (Physiol. Chem.) The action of enzymes; also the changes produced by such action. — Zy•mo•lyt´ic (#), a.

Zymophyte
Zym´o•phyte, n. [ Zyme + Gr. fyto•n a plant.] (Physiol. Chem.) A bacteroid ferment.

Zymoscope
Zy´mo•scope, n. [ Zyme + - scope.] (Physiol. Chem.) An apparatus for determining the fermenting power of yeast by measuring the amount of carbonic acid evolved from a given quantity of sugar.

Zymose
Zy•mose´, n. (Chem.) Invertin.

Zymosis
Zy•mo´sis, n. [NL., fr. Gr. fermentation, fr. ferment.] (Med.) (a) A fermentation; hence, an analogous process by which an infectious disease is believed to be developed. (b) A zymotic disease. [R.]

Zymotic
Zy•mot´ic, a. [Gr. causing to ferment, fr. to ferment, ferment, leaven.]
1. Of, pertaining to, or caused by, fermentation.
2. (Med.) Designating, or pertaining to, a certain class of diseases. See Zymotic disease, below. Zymotic disease (Med.), any epidemic, endemic, contagious, or sporadic affection which is produced by some morbific principle or organism acting on the system like a ferment.

Zythem
Zy´them, n. See Zythum.

Zythum
Zy´thum, n. [L., fr. Gr. a kind of beer; — so called by the Egyptians.] A kind of ancient malt beverage; a liquor made from malt and wheat. [Written also zythem.]