chap, x.] THE THORAX. 151 



that takes place in advancing life. When a rib is 

 fractured, no shortening occurs, the bone being fixed 

 both in front and behind, while vertical displacement 

 is prevented by the attachments of the intercostal 

 muscles. Thus no obvious deformity is produced unless 

 a number of consecutive ribs are the subjects of frac- 

 ture. These bones have been broken by muscular 

 violence, as during coughing, and in violent expulsive 

 efforts such as are incident to labour. In such in- 

 stances the ribs are probably weakened by atrophy or 

 disease. 



In many instances of gun-shot wound the curve 

 of the rib has saved the patient's life. In such cases 

 the bullet has entered behind near the dorsal spine, 

 has been conducted round the chest, along the curve 

 of a rib beneath the skin, and has escaped again near 

 the sternum. This property, however, of the ribs for 

 turning bullets refers rather to the days of round 

 bullets, and not to modern conical projectiles. 



In rickets changes take place at the point of 

 junction of the ribs and cartilages leading to bony 

 elevations, which produce, when the ribs on both sides 

 are affected, the condition known as the " rickety 

 rosary." 



The intercostal spaces are wider in front 

 than behind, and between the upper than the lower 

 ribs. The widest of the spaces is the third, then the 

 second, then the first. The narrowest spaces are the 

 last four. The first five spaces are wide enough to 

 admit the whole breadth of the index finger. The 

 spaces are widened in inspiration, narrowed in expira- 

 tion, and can be increased in width by bending the 

 body over to the opposite side. 



Paraceiitesis is usually performed in the sixth 

 or seventh space, at a point midway between the 

 sternum and the spine, or midway between the 

 anterior and posterior axillary lines. If a lower 



