Wind-Pipe, or Trachea, is a tube composed of cartilaginous rings, and situated in the fore part of the neck, before the gullet. After descending to the. third or fourth joint of the back, it divides itself into two branches, called bronchiae, which enter the substance of the lungs, and there spread themselves in numberless ramifications, terminating in the air-cells, that constitute the chief part of the lungs. Towards the posterior part, the rings are fleshy, or fibrous ; in consequence of which structure, the wind-pipe is enabled to shorten or lengthen Itself, as well as to dilate or contract the diameter of the passage. The internal surface is lined with a very sensible membrane, which, like the whole trachea, is continued from the larynx, being the upper part of the former, below the root of the tongue ; and lubricated by means of numerous glands. This membranous form facilitates the descent of food ; and, by its contraction and dilatation, enables us to expel and admit the air in greater or smaller quantity, and with more or less velocity, as may be required, in speaking or singing. The affections to which this part is exposed, are but few. Thus, if acrid or corrosive vapours, or ex-ilons, have been inspired, demulcents, and mucilaginous drink, for instance, oil, milk, or linseed-tea, should be swallowed in copious draughts, and the steam of the same liquids frequently inhaled; or, the throat ought to be diligently gargled with them, in order to sheath the internal surface, and prevent inflammation. For this purpose, a spoonful of the following mixture should be taken at short intervals; namely, equal parts of sweet-oil, syrup of violets, and honey of roses, properly incorporated. But, if the inhaled vapours have been of a corrosive nature, such as those of arsenic, aqua-fortis, etc. the treatment recommended under the article Arsenic, should be immediately adopted.

Sometimes improper substances, such as crumbs of bread, coarse dust, etc. enter this passage ; and, though they may often be expelled by a fit of coughing ; yet great precaution is necessary, that such effort be not too violent; because ruptures of blood-vessels, or instant suffocation, have often been the melancholy consequence. Should, however, the substances fallen into the. wind-pipe, be pointed, or of large dimensions, they generally produce fatal effects ; unless relief be timely obtained by an operation, which has occasionally proved successful. - See also vol. ii. p. 414.

With respect to inflammation of the wind-pipe, we refer the reader to vol. iii. p. 46-1.