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Rh (M. C. Traub and C. Hock, Ber., 1884, 17, p. 2615). It condenses readily with aldehydes, yielding with formaldehyde, on the addition of, a little hydrochloric acid, methylene diresorcin [(HO)2·C6H3]2·CH2, whilst with chloral hydrate, in the presence of potassium bisulphate, it yields the lactone of tetra-oxydiphenyl methane carboxylic acid (J. T. Hewitt and F. G. Pope, Jour. Chem. Soc., 1897, 71, p. 1084). In alcoholic solution it condenses with sodium acetoacetate to form -methylumbelliferone, C10H8O3 (A. Michael, Jour. prak. Chem., 1888 [2], 37, 470). With concentrated nitric acid, in the presence of cold concentrated sulphuric acid, it yields trinitro-resorcin (styphnic acid), which forms yellow crystals, exploding violently on rapid heating.

In medicine, resorcin, which is official in the United States under the name of resorcinol, was formerly used as an anti pyre tic, but it has been given up. The dose is 2 to 8 grs. Used externally it is an antiseptic and disinfectant, and is used 5 to 10% in ointments in the treatment of chronic skin diseases such as psoriasis and eczema of a' sub-acute character. Weak, watery solutions of resorcin (10 or 15 grs. to the ounce) are useful in allaying the itching in erythematous eczema. A 2% solution used as a spray has been used with marked effect in hay fever and in whooping-cough. In the latter disease 10 minims of the 2% solution has been given internally. It has also been employed in the treatment of gastric ulcer in doses of 2 to 4 grs. in pill, and is said to be analgesic and haemostatic in its action. In large doses it is a poison causing giddiness, deafness, salivation, sweating and convulsions. It is also worked up in certain medicated soaps. Mono-acetyl resorcin, C6H4(OH)·O·COCH3, is used under the name of “euresol.”

Resazurin, C12H7NO4, obtained by the action of nitrous acid on resorcin (P. Weselsky and R. Benedikt, Monats., 1880, 1, p. 889), forms small dark red crystals 'possessing a greenish metallic glance. When dissolved in concentrated sulphuric acid and warmed to 210° C., the solution on pouring' into water yields a precipitate of resorufin, C12H7NO3, an oxyphenoxazone, which is insoluble in water, but is readily soluble in hot concentrated hydrochloric acid, and in solutions of caustic alkalis. The alkaline solutions are of a rose-red colour and show a cinnabar-red fluorescence. A tetrabromresorufin is used as a dye-stuff under the name of Fluorescent Resorcin Blue.

Thioresorcin is obtained by the action of zinc and hydrochloric acid on the chloride of benzene meta-disulphonic acid. It melts at 27° C. and boils at 243° C. Resorcin disrilphonic Acid (HO)2C6H2(HSO3)2, is a deliquescent mass obtained by the action of sulphuric acid on resorcin (H. Fischer, Monats., 1881, 2, p. 321). It is easily soluble in water and decomposes when heated to 100° C.

RESPIRATORY SYSTEM. (1). —The respiratory tract consists of the nasal cavities, the pharynx, the larynx, the trachea, the bronchi and the lungs, but of these the two first parts have been treated in separate articles (see and ).

The larynx is the upper part of the air tube which is specially modified for the production of notes of varying pitch, though it is not responsible for the whole of the voice. Its framework is made up of several cartilages which are moved on one another by muscles, and it is lined internally by mucous membrane which is continuous above with that of the pharynx and below with that of the trachea or windpipe. The larynx is situated in the front of the neck and corresponds to the fourth, fifth and sixth cervical vertebrae. For its superficial anatomy see, Superficial and Artistic.

The thyroid cartilage (see fig. 1) is the largest, and consists of two plates or alae which are joined in the mid-ventral line. At the upper part of their junction is the thyroid notch and just below that is a forward projection, the pomum Adami, best marked in adult males. From the upper part of the posterior border of each aia the superior cornu rises up to be joined to the tip of the great cornu of the hyoid bone by the lateral thyro-hyoid ligament, while from the lower part of the same border the inferior cornu passes down to be fastened to the cricoid cartilage by the crico-thyroid capsule. From the upper border of each ala the thyro-hyoid membrane runs up to the hyoid bone, while near the back of the outer surface of each the oblique line of the thyroid cartilage runs downward and forward.

The cricoid cartilage (see figs. 1 and 2) is something like a signet ring with the seal behind; its lower border, however, is horizontal. To the mid-ventral part of its upper border is attached the mesial part of the crico - thyroid membrane, which attaches it to the lower border of the thyroid cartilage though the lateral parts of this membrane pass up internally to the thyroid cartilage and their upper free edges form the

After D. J. Cunningham, from Cunningham’s Text-Book of Anatomy.

. 1.—Profile View of the Cartilages and Ligaments of the Larynx.

true vocal cords. On the summit of the signet part of the cricoid are placed the two arytenoid cartilages (see fig. 2), each of which

After D. J. Cunningham, from Cunningham’s Text-book of Anatomy.

. 2.—Cartilages and Ligaments of Larynx, as seen from behind.

forms a pyramid with its apex upward and with an anterior posterior and internal or mesial surface. The base articulates with the cricoid by a concave facet, surrounded by the crico-arytenoid capsule, and the two arytenoids are able to glide toward or away from one another, in addition to which each can rotate round a vertical axis. From the front of the base a delicate process projects which, as it is attached to the true vocal cord, is called the vocal process, while from the outer part of the base another stouter process