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DIPHTHONG 371 DIPNOI The ways in which diphtheria bacilli may be conveyed from sick to healthy persons are almost countless. In ordi- nary breathing the expired breath con- tains no germs, but in speaking and especially in coughing, a fine spray is emitted which may contain the bacilli and thus convey the disease. All sorts of articles, such as handkerchiefs, toys, drinking utensils, furniture, clothing, bed- linen and the like, may become contami- nated with the bacilli and be the means of spreading the disease. Hence, pre- ventive measures, consisting in isolation of the patient till the bacilli have disappeared from the throat and in thorough disinfection, are of the first importance in checking the spread of diphtheria. The discovery of the diphtheria bacillus has led to the introduction of a new and most successful method of treatment of the disease, known as serum-therapy or the antitoxin treatment. The establish- ment of the principles and the introduc- tion of this treatment are due especially to Behring of Germany and Roux in Paris. The underlying principle of the treatment is based on the fact that, if a susceptible animal is inoculated first with small and then with increasing doses of the toxin produced by the bacillus, the blood of the animal is found to contain a substance called antitoxin, which has the power of neutralizing or rendering harmless the toxin. In order to obtain large quantities of the healing serum a horse is generally selected for the process of immunization. By proper methods very powerful antitoxins can be obtained. The antitoxin is used not only to cure the disease, but also to render persons in- susceptible for a time to the disease. Dr. William H. Welch, of the Johns Hopkins University, in 1895, in an analysis of over 7,000 cases of diphtheria treated by antitoxin found that the fatality was re- duced by this treatment by over 50 per cent of the previous death-rates. Since his report this conclusion has been con- firmed and even more favorable results have been obtained. DIPHTHONG, two vowel sounds, fol- lowing one another so closely as to form but one syllable, as in out, where the sound is really composed of a and u. Many double vowels in English are not real diphthongs, there being only one sound heard, whereas some single vowels have a diphthongal sound. The only real English diphthongs are i as in high; i in aye; oi in boil; ow in how; and ew in mew. DIPLODOCUS (dip-lod'6-kus), accord- ing to Marsh, a saurian-footed, herbivor- ous dinosaur found in the American Jurassic deposits. The length of skuU of this species was about 21 inches, of brain about 3 inches, and of body 50 feet. The animal is supposed to have been a hippopotamus-like wader, and to have lived on vegetation in the water. DIPLOMA, a writing or document conferring some power, authority, privi- lege, or honor, usually under seal and signed by a duly authorized official. Di- plomas are griven to graduates of a uni- versity on their taking their degrees; to clergymen who are licensed to officiate; to physicians, civil engineers, etc., au- thorizing them to practice their profes- sions. DIPLOMACY, the science or art of conducting negotiations, arranging trea- ties^ and carrying on other important busmess, between nations; the branch of knowledge which deals with the re- lations of independent states to one an- other, the agency or management of envoys accredited to a foreign court; the forms of international negotiations. The Cardinal de Richelieu is generally con- sidered as the founder of that regular and uninterrupted intercourse between governments which exists at present be- tween almost all the Christian powers. Diplomatic agents are of several degrees : (1) ambassadors; (2) envoys extraordi- nary and ministers plenipotentiary; (3) ministers resident; (4) charges d'af- faires; (5) secretaries of legation and attaches. Their rank was regulated in Europe in the above order, by the Con- gress assembled at Vienna in 1814. DIPLOPIA, an affection of the sight, in which objects are seen double. It arises from derangement of the visual axis. DIPLOPTERUS, a genus of fossil ganoid fishes, of four species, belonging to the Old Red Sandstone. DIPLOZOON, a parasitic trematode worm which infests the gills of the bream, and which appears to be formed of two distinct bodies united in the mid- dle, and resembling an x or St. An- drew's cross, two sexually mature indi- viduals being thus united. DIPNOI, an order of fishes, small in number, but of great importance as ex- hibiting a distinct transition between the fishes and amphibia. So many are the points of resemblance between the two, that until recently the Lepidosiren was always made to constitute the lowest class of amphibia. The highest authori- ties, however, now concur in placing it among the fishes. The order Dipnoi is thus defined: the body is fish-like in shape; there is a skull with distinct