DISTANCE. 303 DISTILLATION. In uur daily life, it is perhaps true that the secondary criteria become most important ; tlicy are at least most in evidence. These indirect data of dislanc-e are seven in uunihcr: (1) lin- ear perspective, i.e. the perspective of drawing, the course of the contour lines of objects in the visual field; (2) aerial perspective, i.e. distinct- ness of outline and color-tone; (3) the number of inten-ening objects, or the partial covering of the distant by the nearer; (4) movement of ob- jects in the visual lield, e.g. swiftly moving ob- jects seen from the window of a moving train are known to be near; (5) movement of our own head or body, with consequent relative dis- placement of objects diflerently distant : ( tj) dis- tribution of light and shade, e.g. the illusion of depth given by appropriately shaded stage-set- tings; and (.7) visual angle, i.e. the apparent size of known objects. The two last are the most influential. Consult: Berkeley, An Essay To- uard a Xetc Theury of Vision (London, 1709) ; Wundt, HiDiiiiii and Animal Psychology, trans, by Creighton and Titchener (London, 18'JG) ; Titchener, An Outline of Psychology (New York, 1S99) ; James, Principles of Psychology (New York, 1890). DISTEMPER (OF. destemprer, to distemper, ML. dislvnipcrare, from Lat. dis-, apart + t cm lie rare, to temper, from tenipus, time). A typhoid inflammation affecting the upper air- passages of young dogs, and resembling in many respects the strangles of yoimg horses, and the scarlatina and other »uch complaints of children. Like these, it is contagious, runs a definite course, is accompanied by low fever and debility, and is most successfully treated by good nursing and attention to diet and regimen. The eyes are red. weak, and watery; the nose dry and hot; draughts of air or movements of the ani- mal readily excite sneezing or cough ; there is dullness, fever, and loss of appetite. The thick- ened slimy mucus which the inflamed membrane, after some days, secretes, accumulates about the eyes, nostrils, and respiratory passages, and, lodging in the bronchial tubes, prevents the free access of air and the proper purification of the blood. Hence ensue distressed breathing, increas- ing weakness, and svmptoms of nervous dis- turbance, such as staggering gait, chorea (q.v. ), and fits. All dogs are liable to distemper, but the delicate, highly bred, and artificially treated varieties suffer most severely, and among them the mortality is very great. All irritating and reducing remedies must be carefully avoided, and a good dry bed in a comfortable airy place provided. The stomach, which is generally over- loaded, should be relieved of its contents by an emetic, which for an ordinary-sized Englisli ter- rier may consist of two grains each of tartar emetic and ipecacuanlia. with eight or ton grains cf common salt, given in a wineglassful of tepid water. If no efTect is produced, the dose must be repeated in twenty minutes. Constipation, if present, should be corrected by half an ounce each of castor and olive oil, to which, in large dogs, a few grains of gray powder is a useful addition. The febrile sjinptoms, if acute, may be alleviated by giving four times daily, in cold water, two drops of tincture of aconite, and five grains each of nitre and extract of belladonna. In eases where the pulse is very weak care should be exercised in the administration of aconite. Distressed breathing will be relieved by applying to the chest and sides, for an hour or two continuously, a thick tlanncl cloth, wrung at short intervals out of not water. The throat may also be rubbed with hartshorn and oil, and the nostrils sponged and steamed occasionally. Ciive frequently, and in small quantities at a time, milk and bread, or any other such simple and digestible food; and when recovery is tardy, and weakness ensues, endeavor by nursing, aiid by the use of tonics and stimulants, to support the strength. The term distemper is sometimes applied to in- fluenza (q.v.) in horses, and epizootic pleuro- pneumonia (q.v.) in cattle. For an account of distemper in pigs, see Hog Cholera. DISTEMPER (IX Pai.n-tixg). See Tempera. DISTICH, dis'tik (Lat. disdcftoji, Gk. Sianxov, distichoii, distich, from St-, di-, double -|- crixoc, stichos, row, from uveix^i", steiehein, to tread). The classical name given to any pair of lines, but especially to a hexameter and pentameter, mak- ing complete sense. It was much used by the Greeks and Romans as a vehicle for the expres- sion of single thoughts and sentiments; and hence became almost exclusively employed for the classical epigram. The great poets of mod- ern Germany, Goethe, Schiller, etc.. have also shown a fondness for the distich, and a remark- able skill in the use of it. A collection of moral maxims in Latin, ascribed to a certain Dionysius Cato (q.v.). are called Disticha, and were highly popular during the iliddle Ages. DISTILLATION (Lat. destillatio, from de- stillare, to distil, from de, down + stillare, to drop, from stilla. drop). A process consisting in the evaporation of liquids by boiling and the subsequent liquefaction of their vapors by cool- ing. The purpose of distillation is to separate different substances from one another more or less completely. The process has been in use Kaut{p<u Fig. 1. DISTILLIXO AP- I'ARATCS AS DRAWS IN THE THIRD CENTURY A. D. Fig. 2. DISTILLING APPARA- TUS A8 DRAWN IN THE FIFTH CBKTURY A.D. since ancient times, and in the first centuries of our era was employed in much the same man- ner as at the present time. In the third cen- tury A.D. sea-water was by distillation rendered fit for drinking, and it was known that prac-
