Sex. — The chief difference of external conformation between the sexes is due to the largeness of the mamma?, and the less width across the shoulders in women than in men. There is no distinguishing the sexes by the internal form of the thorax, they so perfectly resemble each other. The chest of the female is only absolutely smaller, but not al ways that, certainly not relatively so. The nipples are not uniformly in the same posi tion ; those of the female are generally closer together than those of the male.
Conformation of the thorax affected by disease and occupation. — The conformation Of the thorax chiefly depends upon the healthy condition of the main pillar of support, the spine ; but not always so, for that deformity called " chicken breast " appears to be inde pendent of the condition of the spine. And, again, emphysema of the lungs tends to pro trude the ribs and advance the sternum.
Disease, as caries of the vertebrm, or an atonic condition of the thoracic muscles, owing to which the spinal column may yield, either laterally, producing " lateral curvature," or an teriorly, giving " angular curvature," produces the most marked distortion of this pillar of support, and consequently of the whole thorax. In 'youth, particularly in females, (from the pre sent system of education,) the spinal column, which is at all times sufficiently flexible, bends under the weight of the head and arms ; and for want of proper exercise the muscles of the back become enfeebled, and unable to restore it to the erect position. When " rickets" attack the spine, it may curve in any direction, com pressing the ribs and projecting the sternum. It is surprising to witness to what an extent of deformity the thorax may attain, and yet life still remain (see fig. 666., where costal respiration could not exist ; and where all the abdominal viscera must have been forced up into the cavity of the thorax, for the 10th rib is nearly touching the crista of the ilium). We have noticed a case where such was the effort of nature to pre serve the thoracic and spinal cavities, that life was maintained in a boy 14 years of age, though 7 bodies of dorsal vertebrm were com pletely absorbed.
In emphysema of the lungs, the sternum is protruded, and the antero-posterior diameter of the thorax is increased sometimes by an inch, the shoulders are raised, and the person assumes always the form of a man who has made the deepest inspiration.
In phthisis puhnonalis, the thorax changes its form, which is manifested by the shoulders inclining forwards, the anterior and superior parts bending in the same direction; the otherwise round full apex becomes flattened, collapsing upon itself; and there is an in capacity to extend the apex ; this is a sure and delicate test of that disease threatening, before any symptoms can be detected by au scultation. In other stages there is a loss of
symmetry in the sides. In pleuritic effusion or in empyema, one side may be full and immov able, whilst the other has to perform the respiratory functions. In fact, disease of the respiratory organs may produce a change in the form of the thorax, either downwards, upwards, or outwards, or by collapse of the apex.
Frequently repeated or permanent compres sion, may produce many varieties of conforma tion of the thorax. Cruveilhier observes that infants, in whom the thorax was perfectly well formed at birth, have become deformed and flattened on the sides of the thorax, by pres sure from the hands of the nurse. Slight ex ternal pressure in early life may be productive of permanent deformity of the thorax, The effect of strong and permanent constriction, as from tight stays, occasions a distortion in the form of the chest. This kind of com pression principally affects the lower part of the thorax ; so that the 5th, 6th, 7th, 8th, 9th, and 10th ribs are pressed forwards and in wards, because the length of their cartilages allow them to yield readily : and the viscera corresponding to these ribs, also undergo alteration in their position and figure, en croaching upon the thoracic cavity, com pressing the lungs upwards, into the apices of the chest. The imprudent custom of females wearing a hard unyielding piece of wood, steel, or whalebone up the front of their corset, commonly produces a compression inwards of the sternum. We once noticed a case where the sternum was forced inwards to such an ex tent, that the entire depth of the thorax, by external measurement, from the middle of the sternum to the corresponding part of the back, only measured 2 inches instead of 8 or 9 inches ! Occupation likewise modifies the form of -the thorax. The clerk who writes many hours at the desk, carries himself dif ferently to the soldier. Coal-miners have stooping chests when they work in districts where the coal seam is thin, and the roof consequently low, as in the north of Eng land. In fact, all trades or occupations which require stooping for many hours to gether, tend to injure and malform the chest.