Page:The American Cyclopædia (1879) Volume VIII.djvu/763

 HISTOLOGY HITCHCOCK 745 general rule, under the microscope, by its size, form, color, consistency, and chemical relations. Thus the striped muscular fibre of the volun- tary muscles, and the smooth muscular fibre of the internal organs, are anatomical elements. The red globules and the white globules of the blood are two different anatomical elements, both mingled with the plasma of the circula- ting fluid. The tendons, ligaments, and perios- teum contain a minute, white, straight, inelas- tic but very strong fibre, which is their most abundant and characteristic anatomical ele- ment. Other membranes and organs contain a larger, flattened, curled, yellowish, elastic fibre, which communicates to them the proper- ty of elasticity in proportion to its own abun- dance. These two kinds of fibre are also distin- guished from each other by their reaction with dilute acetic acid ; the white inelastic fibre be- coming rapidly swollen and transparent by con- tact with this reagent, while the yellow elas- tic fibre is not affected by it. Other anatomi- cal elements which may be enumerated are bone corpuscles, nerve cells, pavement, colum- nar and ciliated epithelium cells, glandular cells, adipose vesicles, cartilage cells, capillary tubes, &c. When two or more kinds of ana- tomical elements are mingled together and in- terwoven in a determinate manner, they form a tissue, just as woollen or cotton threads inter- woven with each other form a web or textile fabric ; and the animal tissues, like artificial fabrics, derive their appearance, qualities, and texture from the number and variety of ana- tomical elements of which they are made up, and the particular manner in which they are interwoven. It is very rare that a tissue con- sists of but a single anatomical element. The tissue of the crystalline lens, containing only flattened fibres with finely toothed edges, and that of cartilage, containing only cartilage cells with an intervening hyaline substance, and cer- tain epithelial tissues, are perhaps the sole ex- amples of this in man and the higher animals. Generally speaking, a tissue consists of several anatomical elements, one of which is peculiar to it, the others perhaps common to several tis- sues. Thus muscular tissue consists of muscu- lar fibres, arranged in parallel bundles, with ultimate nervous filaments and capillary blood vessels ; the bundles themselves being sur- rounded by a thin layer of connective tissue, and associated into secondary and tertiary bundles of larger and larger size, with the trunks and branches of nerves and blood vessels ramifying between them. The liver contains a peculiar anatomical element, the glandular liver cells; but these are arranged in definite groups, form- ing the lobules or acini, with the intra-lobular capillary blood vessels, the commencement of the hepatic ducts, and the terminal filaments of the hepatic plexus of the sympathetic nerve. In the study of histology the different powers of the microscope are employed for different objects. The highest powers are generally re- quisite for the examination of the ultimate ana- tomical elements. But in order to learn in what form these elements are associated with each other, or how they are interwoven with still different ones to ascertain, in short, the struc- ture of the tissue the lower powers must be employed; since a very highly magnifying lens can only be used when the tissue has been mi- nutely subdivided, and this destroys of course the natural arrangement of its parts. Certain artificial aids and contrivances are often also of great value in bringing into view peculiari- ties of texture which would otherwise remain invisible, such as the injection of minute vessels with colored fluids, and the staining of the tis- sue with certain reagents, such as iodine, ni- trate of silver, and the like, which will attack some of its anatomical elements and leave others entirely or comparatively unaffected. Thus two different anatomical forms which were originally so similar in color, consistency, and refractive power that they could not be dis- tinguished by the microscope, may have their outlines made visible and easily recognized in the surrounding parts. These manipulations, however, should be used with great caution and judgment; otherwise deceptive appearances, produced by the action of reagents, such as the shrivelling of membranes, the contraction or enlarging of fibres, or the coagulation of soft material, may sometimes be mistaken for the natural characters of the tissue. The best works on histology, often called microscopic anatomy, are those of Kolliker, HandbucJi der Gewebelehre (Leipsic, 1852 ; translated by Busk and Huxley, Sydenham society publications, London, 1853, and Philadelphia, 1854); Peas- lee, "Human Histology" (Philadelphia, 1857); and Strieker, Lehre von den Geweben des Men- schen und der Thieve (Leipsic, 1869-' VI). HIT (anc. /), a town of Asiatic Turkey, in the vilayet and 70 m. W. N. W. of the city of Bagdad, on the W. bank of the Euphrates; pop. about 2,000. It is situated on a hillside, and the streets are narrow, dirty, and often steep. The houses are chiefly of clay, one or two stories in height. A graceful minaret and some tombs are the only buildings worthy of notice. The inhabitants are employed in boat building and the preparation of wool, salt, naph- tha, and bitumen, for which last the place has been famous for ages. Thothmes III. brought bitumen from Hit to Egypt about 1400 B. C. According to Herodotus, the bitumen of Is was used in the building of Babylon. HITCHCOCK, a S. W. county of Nebraska, re- cently formed, and not included in the census of 1870 ; area, 720 sq. m. It borders on Kan- sas, and is watered by the Eepublican river. HITCHCOCK, Edward, an American geologist, born in Deerfield, Mass., May 24, 1793, died at Amherst, Feb. 27, 1864. He was principal of the academy in his native place from 1815 to 1818; pastor of the Congregational church in Conway, Mass., from 1818 to 1825; professor of chemistry and natural history in Amherst college from 1825 to 1845 ; president of the