1. Deficiency And Excess Of Development

The full growth of the thorax is arrested in various degrees in monsters which are very incompletely formed; especially in those which are also acephalous or anence-phalous, or which are born with spina bifida. The malformation of the thorax is in these cases associated with a corresponding deficiency, or a small and ill-developed state of the lungs and heart, and with hernial protrusion of those organs. It may arise either from partial absence of the spine, from fusion of some of the dorsal vertebrae together, from deficiency or incomplete development of the ribs, or from fission of the thorax and abdomen; and it consists in diminution of size and capacity, and generally, also, in misshapen exterior.

But, sometimes, persons, otherwise well formed, lack one dorsal vertebra, and one - generally the twelfth - rib; in a few instances, indeed, one or more ribs are found wanting, even when the number of vertebrae is complete. Occasionally, though there may be a proper complement of ribs, one of them is too short, and instead of reaching the sternum, it ends in a pointed cartilage.

Now and then there is no sternum, or only a part of it exists; or it is fissured at one spot, or in its whole length. The last condition is just indicated in some well-formed persons, whose ensiform cartilage is split or perforated, or in whom the lateral ossific centres in the body of the sternum remain separate for a long time. When the bone is wanting altogether, its place may be supplied, and the thorax closed by a firm fibrous membrane; otherwise, whether the opening be formed by a total or partial absence, or by a mere fissure of the sternum, the thoracic organs will protrude. Moreover, the bone may be unnaturally short, small, narrow, or the like.

In those double monsters in which the point of junction is the thorax, that part is found developed to excess. It is perternaturally developed likewise, when there is more than the proper number of ribs. Sometimes the supernumerary rib is borne upon a thirteenth dorsal vertebra, sometimes upon the first lumbar, while, in rare cases, the seventh cervical vertebra has a rib connected with it, which may either terminate by a free extremity, or become attached to the sternum, or to the true first rib. Some ribs are so broad as to appear double; others are fissured at different parts; while others, again, are forked at their anterior extremities, etc.

2. Deviations From The Natural Size And Form Of The Thorax

The chest is subject to several other varieties in size, or capacity, besides those which have been already mentioned: some of them are faults of original conformation, and are either connected with peculiarity in the general organization of the individual, or have a more immediate relation to some anomaly in the viscera of the trunk; while others arise from disease of the lungs, or pleura, or of the respiratory muscles. Whether the deformity be one of enlargement, or contraction, it may affect the two halves of the chest nearly or quite symmetrically, or it may be confined to one half, or even to a still less portion of it: but the change of form is greatest, when it occupies only a half, or a still smaller section, of the chest. The following are the principal deformities.

In some men the whole skeleton approaches, in its general form, the type which is characteristic of the female; and the thorax, as well as the pulmonary organs, are of small size. This individual peculiarity is the more marked, in proportion as the abdomen, more particularly, resembles the largely-developed abdomen of the woman. On the other hand, men are met with now and then, whose chests are disproportionately large and capacious.

Contractions of the chest, both when they are symmetrical, and when confined to one part, are observed in cases of pneumonia in which the lung is wasted, in catarrh and dilatation of the bronchi, in tuberculosis and tubercular phthisis in the lung, in pleurisy, and in paralysis and atrophy of the inspiratory muscles at the upper, anterior, and lateral parts of the chest, etc.

Dilatations Ensue From Emphysema Of The Lung

Dilatations Ensue From Emphysema Of The Lung, from pleuritic effusion, pneumothorax, and considerable effusions into the pericardium, from enlargement of the heart, dilatations of the aorta, large growths in the chest, etc.

The varieties in the form of the thorax present more interest than those of mere size, though the two are combined in numerous ways.

It is unnecessary to repeat, though it is desirable to refer to, what has been said, with regard to the deformities of the thorax connected with curvatures of the spine: the chief of those which remain are as follow:

The compressed and shallow chest, flattened from before backwards, which the clavicles and projecting shoulders overhang like wings, and which expresses the phthisical constitution. There is no question, that a thorax of this form is often associated with a peculiarity of the whole organization; but it is the latter, and not the form of the thorax, which predisposes to tubercular disease of the lungs. What such a chest loses in breadth and vaulted form, it gains in length; its capacity is by no means necessarily deficient, nor is that of the lungs within it; and that such a form of chest gives a predisposition to phthisis, is quite hypothetical.

The thorax is sometimes flattened, or even depressed, in the subclavicular regions, and thus obtains the phthisical form. This change is a consequence of wasting of the pulmonary tissue in the vicinity of tubercles, or of closure of vomicae in the apices of the lungs: it also sometimes results from pleurisy in the same region.

In general emphysema of the lungs, the chest is enlarged, and acquires a vaulted barrelled shape.

After the subsidence of chronic inflammation of one whole pleura, the corresponding half of the chest becomes flattened; or it may even sink in and form a kind of pit. If the pleurisy have been confined to a part of the membrane, a similar deformity takes place, but occupies only that portion of the chest. In the former case the ribs fall in, especially at their anterior extremities, and lie so close together along their whole length, that the interspaces between them are obliterated; and the diameter of the chest is diminished on that side in every direction. The consequence is, that the dorsal vertebrae curve towards the opposite or sound side of the chest, and that a curvature of compensation takes place in the lumbar region; at a later period of life it may even be found that the deviation of the spinal column has reached the pelvis and rendered it oblique.

There is a remarkable deformity of the chest which is known by the name of pigeon-breast. The cause of it is an attenuated condition of those muscles of inspiration which are situated at the upper, anterior, and lateral regions of the chest, viz., the pectorales and serrati; and it is very frequently, though not constantly, combined with rickets of the thorax. The chest is flattened laterally; and very frequently it has even a longitudinal depression towards the anterior extremities of the bony ribs, while the sternum, with the costal cartilages, strongly curved, projects considerably in front (pectus carinatum). The spine is either straightened, or presents a slight excurvation. The diaphragm becoming hypertrophied, carries on the respiration, and makes up for the diminished breadth of the chest by increasing its vertical diameter. The depression of the diaphragm considerably augments the size of the abdomen externally: and as the latter circumstance has chiefly arrested the attention of observers, it has led to numerous misconceptions as to the true theory of the disease. The ribs frequently bear the clearest marks of rickety disease of their tissue; and even in life the enlargement of their anterior extremities may be easily perceived.

Another, and an important deformity of the thorax, is that in which it becomes narrowed and cylindrical, and, at the same time, elongated. The change arises from paralysis of the intercostal muscles, and is produced by enlargement of the inferior intercostal spaces. It has been named by Engel the paralytic thorax (Oesterr. Jahrb., April, 1841).

The contraction of the thorax which takes place in old age is sometimes allied to one, and sometimes to the other of the two last-described deformities.

The chest sometimes becomes misshapen in consequence of following certain employments and trades: thus shoemakers have a depression at the lower end of the sternum.

Amongst the peculiarities of the several parts of the chest, there are still those of the ensiform cartilage which require notice. The most remarkable is the inversion of a long processus ensiformis.

3. Solutions Of Continuity

Fractures of the ribs are of serious moment, from their sometimes injuring the pleura and lungs, and even the pericardium and the heart. Single fractures, for the most part, unite readily, but when several successive ribs are broken, false joints are sometimes formed between the tumors of callus thrown out around their fragments. Fractures of the sternum are usually transverse; they seldom occur unless the ribs or spinal column are injured at the same time.

4. Hyperostosis, Atrophy

The spongy exostosis sometimes presents itself on the ribs and sternum as an example of hyperostosis. Atrophy of the ribs is commonly well marked in tabes senilis of the skeleton; and both ribs and sternum are frequently worn away, and even perforated by the pressure of aneurisms of the ascending part, and arch of the aorta.

5. Abnormal Changes Of Texture

Caries and necrosis are frequently met with in the ribs and sternum. They are often produced by empyema and suppuration in the pleura, by the softening of tubercular lymphatic glands, by vomicae of the lungs arising from tubercle, etc. The inflammation and induration which occur in syphilitic disease are rarely met with in the sternum.

Morbid growths are rather frequent both in the sternum and ribs; and they present the various forms of enchondroma, tubercle and tuberculous caries, and of cancer; the last may be a consequence of the degeneration of that disease in the adjoining glands of the chest, or a substantive new growth in the bones themselves.