HISTOLOGY. lOf? HISTORY. a firm mass, which can l>e easily cut. For thiss purpose paratlin and celloidin are most commonly used. In paraffin imliedding, the tissue is tirst immersed in any pure solvent of imraffin. then passed to a warm solution of paraffin in the solvent, and finally left in pure melted paraf- fin, until thoroughly impregnated, in celloidin imhcdding the tissue is transferreii from alcohol to a nii.ture of alcohol and ether, and then placed in a solution of celloidin in a mi.xture of equal parts of alcohol and ether. After impregnation the paraffin is allowed to harden hy cooling, or the celloidin to thicken by exposure to the air and consequent evaporation of the alcohol and ether, after which it is immersed in chloroform for hardening. The operator then |)roceeds to cut sections by means of the microtome. This in- strument consists essentially of a knife-carrier, which can be made to slide back and forth past a clamp to which the specimen is attached. The imbedded specimen is fastened to a block, usual- ly of wood, clamped in the microtome. The clamp is so arranged that the blocked specimen can be raised any desired fraction of a milli- meter, thus bringing any thickness of it above the knife. In paraffin-cutting the knife is kept dry ; in celloidin section-cutting it is kept flooded with alcohol. 'Ilie sections are then stained for the purpose of bringing out sharply the different tissue elements. For staining the nuclei, car- mine, ha-matoxylin, and various aniline dyes are commonly used. For demonstrating the other tissue elements other dyes may be used, eosin 1m>- ing much used. The procedure in staining cel- loidin sections with hipmatoxylin and eosin is as follows: The sections are first allowed to remain for several minutes in an aqueous solution of hipmatoxylin ; then they arc thoroughly washed with 97 per cent, alcohol, and placed for several minutes in an alcoholic .solution of eosin; they are then again washed in alcohol and cleared in oil of origanum or bergamot containing a little eosin. From the clearing bath the specimen is lifted to a glass slide, the excess of oil is re- moved by means of blotting-paper, a drop of a solution of Canada balsam is placed upon the specimen, and the whole is covered with a thin glass, called the cover-glass. By the drj-ing and hardening of the balsam a permanent 'mount' of the specimen is secured. The above methods of procedure are illustra- tive of those applicable to general histological material. The examination of special tissues and organs requires the use of special methods of technique. This is especially true in regard to the nervous tissues, for the study of which some very elaborate methods have been devised, some of which will be found described in the article Nervois Svstem. For histological methods as applied to plant tissues, consult Chamberlain, Methods in Plant Hintolofi!/ (Chicago. 1001) ; for methods in ani- mal liistology. consult Lee, Microtomist's Vade- mecum. (London, 18fl0). HISTORICAL ASSOCIATION, .Xmerican. A society of historical students and writers, founded at Saratoga, X. V.. in September. 1884, at the suggestion of Herbert B. ,dams. of Johns Hopkins Lniversity. Its original member- ship was 40, but within a year it had increased to •250. and in ls80 it received a definite standing and recognition ny an act of Congress incorporat- ing it in tiie District oi Columbia. The society has exerted wide influence in directing and stimu- lating historical research, and its publications and monographs have covered a broad field of historical study. Allied with the .society is the American Society of Church History. This or- ganization, founiled in Jlarch, 1888, liecamc the Church History Section of the Historical Society in 1889. Another important branch of the so- ciety is the Historical Manuscripts Commission, which prepares valuable manuscripts for publica- tion. The society holds annual meetings, and pub- lislies an annual report through the Smithsonian Institution at Washington. These reports include historical articles and bibliographies, and the society publishes in addition many monographs. As examples of the latter maj- be mentioned: Federal Land (irants in the United States, by George V. Knights: Church and Slate in the United States, by I'-hilip Schatf: ^Villem Ussr- linx. by .J. I". .Jameson; The Continental Con- gress, by Herbert Fricdcnwald; and The Stud;/ of History in Schools, by a s])ecial committee of seven, appointeil by the society. The presidents of the society have included eminent .Vmerican historians. They have been : .Xndrew D. White, (ieorge Bancroft, .Justin Winsor, William F. Poole, .Tames Schouler, George F. Hoar, Edward Eggleston. and .Alfred T. Mahan. Tlie member- ship is about 1400. HISTORICAL SOCIETY, Royal. A learned association in London, louiided in 18(18, and in- corporated .July ;il, 1889. with the object of pro- moting the study of history. Us membership, which is international, nunil)ers about fiOO, di- vided into Fellows, Honorary Fellows, and Cor- responding Members. On .Ma"y 2, 18!1(>. the Royal Historical Society amalgamated with the Cam- den Society (q.v.). The Royal Society publishes annual volumes of Transactions and Uocuments, which are distributed without charge to mem- bers. HISTORIC GEOLOGY. See Geoloot. HISTORY (Lat. hisloria, Gk. laropla, hi.story, from uTTwp, histor, learned, from tiiivat, cidenai, Skt. lid, UIIG. trizzan. (Jer. nissen, to know). A systematic narrative of past events, or. in the light of modern historical scholarship, the .science of the progressive development of human society. The social and economic conditions of peoples, their racial aflinities and physical environment, exercise determining influences upon their his- tory, and find expression in their thought, their art', and their politics. History deals with the social structure in its successive forms and rec- ognizes as inseparable allies all .sciences which contribute to a knowledge of man as a social being, and in his relation with the physical world. .As a science, history is primarily inductive. It proceeds from a body of cr)nerete facts, which critical study links togetheT according to the sequences of time and causation. .-Vfterwards deductive processes may be used, but always sparingly and cautiously. Historical methml comprises four processes : the collation of facts; the arrangement of these facts, according to the sequences of time and causation: criticism, by which the value of the facts is determined; and their interpretation in accordance with the results of arrangement and criticism. These processes are all simple: they are the ordinary processes of scientific research, but in carrying them out the human equation
