Page:The New International Encyclopædia 1st ed. v. 05.djvu/808

CYANOGEN. 700 CYANOSIS. ogen groups' (CN, or, as it is often written, Cy), which enter into the composition of a large number of other substances known. Some of these interesting substances having a blue color, the name cyanogen has been applied to the gas from which they are derived ; but that gas itself is perfectly colorless. During the preparation of cyanogen from the cyanide of mercury, an amorphous brown substance forms, which has the same percentage composition as cyanogen, but ))robably a much higher molecular weight: this compound is called paracyanogen and is denoted by the symbol (CN)x. Paracyanogen may be readily transformed into cyanogen gas by heating. The derivatives of cyanogen form a large group of compounds, including hydrocyanic acid and its salts, the fcrro-cyanides and ferri-cj'an- ides, cyanic and cyanurie acids and their deriva- tives, etc. The most important of these com- pounds are described in special articles. CY'ANOI'DEA (Neo-Lat. nom. pL, from Gk. (cfawf, l:i/aiios, dark-blue + eidoc, eiclos, form). A suborder of the Carnivora (q.v. ), composed of the family Canids (dogs, wolves, jackals, etc.), regarded as forming the most central group of the Carnivora, from which the bears, weasels, and raccoons (Arctoidea) depart on the one hand, and the cats, civets, and hyenas (Ailu- roidea ) depart on the other. . Consult Huxley, Anatomy of Vcrtc^irated Animals (New Yorl<, 1878). and the books mentioned under Mam- malia. Dog, Fox, etc. CY'ANOM'ETEE. (Gk. Kiavog, kyanos, dark- blue + /ztTpoi', met run, measure). An instrument for determining the color of the sky, invented by Saussure — a disk divided into sections, the sev- eral sections being tinted and gradually increas- ing in intensity from white to deep blue. When used to compare with the color of the sky, some of its sections will appear deeper and some lighter in tint. The section where there is no perceptible dilTerence gives the measure or degree of the bluencss of the sky. CY'ANOPHY'CE^ (Neo-Lat. nom. pi., from Gk. Kiiamc, kyanos, dark-blue + (pvKog, phylcos, seaweed ) . The lowest of the four great groups of alg;B. They are called blue-green algae from the prevailing color of the cell contents, which are tinted by a diffused blue pigment named phycocyan. The cell -structure is very simple, agreeing in this respect with the Bacteria (q.v.). For details of cell-structure and elassi- fiaation, see Alg.e. Many of the Cyanophycea^ are one-celled, or consist of indefinite aggregations of cells situated in a conniuin gelatinous matrix. Other forms are filamentous, and some are elaborately branched. A well known unbranched form is Oscillatoria, interesting because of the move- ments of the tip of the filament, which swings in a circle. Nostoc forms large gelatinous balls filled with convoluted chains of cells. Certain cells in some filamcnlous forms lose their protoplasmic contents, becoming the so-called heterocysts, whose functions are not well understood; but they are responsible in many cases for the branching of the filaments, because the hetero- cysts become firmly fastened to the sheaths that inclose the vegetative cells. The gro^vth of the latter causes such pressure betAveen the fixed noints, determined by the heterocysts, that the sheath is ruptured and the filament grows out at one side. Such branching is termed 'false branching.' Branches or portions of filaments that bi'eak off and start new plants are called hormogonia. The Cyanophycea; are especially fond of wurni shallow water, although many grow in damp sit- vuitions on land, such as spray-wet rocks, damp timber, and earth. They live among the reeking vegetation of salt marshes, and flourish in open sewers and drains. The fouling of shallow res- ervoirs in warm weather, when they give off the well-known 'pig-pen odor,' is generally due to growth of CyanophyceiE. The only remedy is to deepen the water. One of the most remarkable displays of Cyano- phyceoo is in warm springs, well illustrated in Yellowstone National Park, where' the growths are brilliantly colored. Here certain species grow luxuriantly in water at a temjjerature of 75° C. and above, conditions which no other forms of algie can endure. Another conspicuous display of blue-green algiE is the water-bloom or scum that fre- quently covers the surface of ponds and small lakes, ilost of the water-blooms are due to CVAXOPHYCEj;. 1, a and h, Osoillatoria ; 2, Chroococcus (a), and its division (b) : 3, Stigonema, showing false brandling and lieterocysts. Cyanophyceap, and the largest of all has given name to the Red Sea, whose tint is due to the presence of a fiocculent sediment made up of bundles of short filaments of Trichodesmium. This peculiar condition of the ocean is not eon- fined to the Red Sea, but has been reported off the coast of Brazil and South Carolina, and in the Indian and Pacific oceans. The best monograph on the Cyanophyeea^ is Bornct and Flahault. T^osiocacces Bcferocystces (Paris. 18SG-S8). CYAN'OPHYLL (Gk. kHupoc, kyanos, dark- blue -f (pi?.Anv, phyllon, leaf). A collective name for the lihic coloring substance of leaves and flowers. Sec Color. CY'ANO'SIS (from Gk. Kfei'of, kyanos, dark- blue). Lividity of the skin, caused by interrup- tion of the circulation or of the respiration. It may be temporary, as in a convulsion, when the face or lips are blue, or in croup (q.v.), where