Chest

Chest. The cavity of the chest or thorax is bounded posteriorly by the spinal column and anteriorly by the sternum, is walled in by the ribs and intercostal muscles laterally, and is separated below from the cavity of the abdomen by the diaphragm. Above, the circumference of the chest rapidly narrows, so that the superior aperture of the thoracic cavity is of less dimensions than a transverse section at any lower level. Through this aperture pass the trachea or windpipe and oesophagus, as well as important blood-vessels and nerves. A transverse section at the level of the lower part of the sternum is roughly elliptical in shape. A series of measurements of the healthy adult male chest taken at this level gives, as average results, the following figures: - Circumference, 35 inches; antero-posterior diameter, 9 inches; transverse diameter, 11 inches. The chest is never quite symmetrical, the right half being usually somewhat larger than the left, in association with the greater development of muscles on the right side of the body. Certain deviations from the normal shape of the chest are met with in disease. The flat chest and the pterygoid chest are often found in association with phthisis (consumption). The pigeon breast results usually from prolonged chest mischief in childhood, for oft-repeated paroxysms of coughing, if they occur at a time when the ribs have not acquired the relative inflexibility of the adult condition, cause a straightening of the anterior part of the ribs, and thrust the sternum forward, leading to the shape of chest which has been compared to that, which obtains in the bird. A transverse furrow known as Harrison's sulcus is also often produced in those who as children had "delicate chests"; the most common deformity of the chest is, however, the rickety chest. Curvature of the spine produces, of course, a deviation from the natural shape of the chest. In the thoracic cavity are contained the lungs and the heart with the vessels entering and leaving it. The oesophagus traverses the whole length of the chest to leave it below by an aperture in the diaphragm; and by its side through the greater part of its course runs the thoracic duct. The spaces lying in front of and behind the heart, and unoccupied by the lungs, are called the anterior and posterior mediastina respectively.