THE COSTAL CARTILAGES 167 



small portion of its extent. At the back the angles of the ribs form a slightly marked oblique 

 line on each side of and some distance from the vertebral spines. This line diverges some- 

 what as it descends, and external to it is a broad, convex surface caused by the projection of 

 the ribs beyond their angles. Over this surface, except where covered by the scapula, the 

 individual ribs can be distinguished. 



Applied Anatomy. Malformations of the sternum present nothing of surgical importance 

 beyond the fact that abscesses of the mediastinum may sometimes escape through the sternal 

 foramen. Fractures of the sternum are by no means common, .due, no doubt, to the elasticity 

 of the ribs and their cartilages, which support it like so many springs. When broken it is fre- 

 quently associated with fracture of the vertebral column, and may be caused by forcibly bending 

 the body either backward or forward until the chin becomes impacted against the top of the 

 sternum. It may also be fractured by direct violence or by muscular action. The fracture 

 usually occurs in the upper half of the body of the bone. Dislocation of the gladiolus from the 

 manubrium also takes place, and is sometimes described as a fracture. 



The bone, cancellous in structure and being subcutaneous, is frequently the seat of gumwa- 

 tous tumors, and not uncommonly is affected with caries. Occasionally the bone, and especially 

 its ensiform appendix, becomes altered in shape and driven inward, in workmen, by the 

 pressure of tools against the chest. 



The ribs are frequently broken, though from their connections and shape they are able to 

 withstand great force, yielding under the injury and recovering themselves like a spring. The 

 middle of the series are the ones most liable to fracture. The first, and to a less extent the 

 second, being protected by the clavicle, are rarely fractured; and the eleventh and twelfth, on 

 account of their loose and floating condition, enjoy a like immunity. The fracture generally 

 occurs from indirect violence, from forcible compression of the thoracic wall, and the bone then 

 gives way at its weakest part i. e., just in front of the angle. But the ribs may also be broken 

 by direct violence, when the bone gives way and is driven inward at the point struck, or they 

 may be broken by muscular action. It seems probable, however, that in the latter case the 

 bone has undergone some atrophic changes. Fracture of the ribs is frequently complicated by 

 some injury to the viscera contained within the thorax or upper part of the abdominal cavity, 

 and this is most likely to occur in fractures from direct violence. Occasionally supernumerary 

 ribs exist. They may come from the lumbar vertebrae or from the cervical vertebrae. A lumbar 

 rib does not cause discomfort. 1 A cervical rib is due to excessive development of the costal ele- 

 ment of the seventh cervical vertebra. In nearly two-thirds of the reported cases the condition 

 is bilateral. It rarely produces symptoms until after the twentieth year. The symptoms are a 

 superficial pulsation of the subclavian artery, a prominence which can be felt, and evidences of 

 pressure in the brachial plexus (Carl Beck). Beck divides the different types of the condition as 

 follows: "(a) Slight degree: The cervical rib reaches beyond the transverse process, (b) More 

 advanced: The cervical rib reaches beyond the transverse process, either with a free end or 

 touching the first rib. (c) Almost complete: The connection between the cartilage of the first 

 ril) is formed either by means of a distinct band or by the end of its long body, (d) Complete: 

 It has become a true rib and possesses a true cartilage which unites with the cartilage of the 

 first rib." 2 A very rare condition is a rib from the sixth cervical vertebra. The diagnosis is 

 confirmed by the .r-rays. The treatment of cervical rib is excision. 



Fracture of the costal cartilages may also take place, though it is a comparatively rare injury. 



The thorax is frequently found to be altered in shape in certain diseases. The shape 

 of the thorax in those suffering from rhachitis is produced chiefly by atmospheric pressure. 

 The balance between the air on the inside of the thorax and the air on the outside during 

 some stage of respiration is not equal, the preponderance being in favor of the air outside; 

 and this, acting on the softened ribs, causes them to be forced in at the junction of the carti- 

 lages with the bones, which is the weakest part. In consequence of this the sternum projects 

 forward with a deep depression on either side caused by the sinking in of the softened ribs. 

 The depression is less on the left side, on account of the ribs being supported by the heart. The 

 condition is known as pigeon-breast. The lower ribs, however, are not involved in this deform- 

 ity, as they are prevented from falling in by the presence of the stomach, liver, and spleen. And 

 when the liver and spleen are enlarged, as they sometimes are in rhachitis, the lower ribs may be 

 pushed outward; this causes a transverse constriction just above the costal arch. The anterior 

 extremities of the ribs are usually enlarged in rhachitis, giving rise to what has been termed the 

 rhachitic rosary. The phthisical chest is often long and narrow, flattened from before backward, 

 and with great obliquity of the ribs and projection of the scapulas. In pulmonary emphysema 

 the thorax is enlarged in all its diameters, and presents on section an almost circular outline. It 

 has received the name of the barrel-shaped chest. In severe cases of lateral curvature of the 

 spine the thorax becomes much distorted. In consequence of the rotation of the bodies of the 

 vertebrae which takes place in this disease the ribs opposite the convexity of the thoracic curve 

 become extremely convex behind, being thrown out and bulging, and at the same time flattened 



1 Carl Beck, in Jour. Amer. Med. Assoc., .Tune 17. 1905. - Jour. Anier. Med. Assoc., June 17, 1905. 



