THE THOEAX. 1397 



certain definite regions or areas. The vertical lines are : the mid-sternal, the 

 lateral sternal, the para-sternal, the mammary or mid-clavicular, the anterior, mid, 

 and posterior axillary, and the scapular. The position of the mid- and lateral 

 sternal lines is sufficiently indicated by their names. 



The mammary, better termed the mid-clavicular, is drawn vertically downwards 

 from the centre of the clavicle, or, what comes to practically the same thing, from a 

 point midway between the centre of the jugular notch and the tip of the acromion. 

 In the male this line usually lies J to j in. medial to the centre of the nipple, 

 which is usually placed over the fourth interspace, or fifth rib, four inches from 

 the median plane. In the child the nipple may be as high as the inferior border of 

 the third rib. In the female the position of the nipple is so variable that it is of 

 no topographical value. In a well-proportioned subject, the mid-clavicular line, if 

 prolonged downwards, will be found to be continuous with the vertical or lateral 

 inguinal line, which crosses the costal margin at the tip of the ninth costal cartilage. 



The para-sternal line, drawn midway between the lateral sternal and mid- 

 clavicular, crosses the costal margin opposite the tip of the eighth costal cartilage. 



The anterior, the mid, and the posterior axillary lines are drawn downwards 

 from the anterior fold, the apex, and the posterior fold of the axilla, respectively. 



The scapular line is drawn perpendicularly through the inferior angle of the 

 scapula. 



Of the two transverse lines, the superior, which separates the infra-clavicular and 

 supra-sternal regions from the mammary and infra-sternal regions, is drawn at the 

 level of the third chondro-sternal articulation ; the inferior, which separates the 

 mammary and infra-mammary regions, is drawn at the level of the sixth chondro- 

 sternal articulation. 



The lateral area of the chest is divided into a superior, or axillary, and an inferior 

 or infra-axillary region, by a horizontal line drawn at the level of the sixth rib. 



In muscular subjects there is a well-marked median furrow, the sternal furrow, 

 between the sternal origins of the pectoralis major muscles. The medial part of the 

 inferior border of each of these muscles forms a curved prominence which, overlying 

 the fifth rib, corresponds to the junction of the mammary and infra-mammary 

 regions. Below this prominence is the infra-mammary region, which forms a 

 somewhat flat surface, corresponding to the upper part of the rectus muscle. In 

 the axillary and infra-axillary regions are the prominences caused by the digitations 

 of origin of the serratus anterior, the first to appear below the pectoralis major 

 being that which springs from the fifth rib. 



The superior border of the sternum lies in the same horizontal plane as the 

 inferior border of the body of the second thoracic vertebra, the distance between the 

 two being about two inches. The junction of the manubrium and the body of the 

 sternum forms a slight prominence or angle, known as the angulus sterni 

 (Ludovici), which, although not usually visible, may always be felt. The angulus 

 lies in the same plane as the body of the fifth thoracic vertebra. 



The xiphi-sternal junction corresponds to the fibro-cartilage between the ninth 

 and tenth thoracic vertebrae. Immediately inferior to the xiphi-sternal articulation 

 is the infra-sternal notch, formed by the junction of the seventh costal cartilages 

 with the sternum. Inferior to the notch is the epigastric fossa or triangle, bounded 

 laterally by the seventh costal cartilages. The apex of the triangle forms an angle 

 which varies considerably according to the shape of the chest, the average being 

 about 70. Not infrequently the eighth costal cartilage articulates with the sternum. 



Fracture of the sternum is rare, and generally occurs at or close to the junction of the manu- 

 brium and the body ; it may occur either from direct violence, or indirectly along with fracture 

 of the vertebral column. Unlike that of the ribs, the periosteum covering the sternum is firmly 

 adherent to the bone. 



The ribs, which in well-nourished subjects cause no surface prominences, are 

 readily visible in thin persons ; in the obese they are very difficult to feel. In 

 counting the ribs from the front, the second may always be identified by its relation 

 to the angulus sterni. The first rib is to a large extent under cover of the clavicle. 

 The inferior border of the pectoralis major and the first visible digitation of the 



