ZYLONITE (from Gk. ξύλον, xylon, wood). A substitute for ivory, made by treating vegetable fibre or cellulose with a mixture of nitric and sulphuric acids, dissolving the resulting pulp in a suitable solvent, such as camphor, and drying the product. In 1855 such a compound was in- vented by Alexander Parkes of Birmingham, England, and put on the market under the name of parkesinc. Factories were established in vari- ous places in Europe for the manufacture of similar compounds, which were generically called zj-lonite, but they were not successful. In 1SG9 John W. Hyatt, of Newark, N. J., began the manufacture of a product made similarly to the foregoing and called it celluloid. This has since largely superseded all other varieties of zylonite. See Celluloid.
ZYMASE (from Gk. fu/iij, ?i/me, leaven). An enzyme (q.v.) discovered by Buchner in the com- mon yeast (Saccharomyces cerevisiw). It acts upon the products of inversion by invertase (q.v.) and breaks up these sugars into carbon dioxide, alcohol, water, and some less important products.
ZYMOT'IC DISEASE (Gk. fo;iuTiK6s, zymo- tikos, causing to ferment, from ^/xwo-is, zymosis. fermentation, from t^v/xoOv, zymoyn, to fermentj from ivjiTi, zymC, leaven, from iUiv, zeein, to boil). An old term for a disease supposed to be caused by fermentation of a substance received into the body, and formerly applied to smallpox, typhoid fever, plague, influenza, etc. Under the intluence of the new science of bacteriology the zymotic was transformed into the zj'uiotoxic theory of infectious disease, and the former term has largely fallen into disuse. See Disease, Gebm Theory of; Miasma; Kosology.
ZYR'IANS. A Finno-Ugrian tribe, numbering 30.000. living on the headwaters of the Dvina and Petchora, in Russia, where they are settled along the navigable streams. They are brachycephalic, the index being 82.2. Hunting is the chief occu- pation, but as traders they visit the fairs of North Russia over a wide radius. They are now Russianized, and the old nature worship which they formerly practiced has almost passed away, one of the traces of it being the sacrifices of ani- mals before the churches. Formerly these sacri- fices were made in birch groves, which were held sacred, and in them was carried on the worship of a being called the 'Old Woman of Gold."
