172 SURGICAL APPLIED AWATOMY. [Chap. x. 



two parts of the bone are not entirely united until 

 middle life, and are often not united at all, it follows 

 that the lesion is in many cases a dislocation rather 

 than a fracture. The manubrium in these injuries 

 generally remains in situ, while the gladiolus with the 

 ribs is displaced forwards in front of it. Malgaigne 

 cites the case of a youth who, from constant bending 

 at his work as a watchmaker, caused the second piece 

 of the sternum to glide backwards behind the manu- 

 brium. Here, probably, the connection between the 

 two bones was not very substantial. 



From its exposed position and cancellous structure, 

 the sternum is liable to many affections, such as caries 

 and gummatous periostitis. The comparative softness 

 also of the bone is such that it has been penetrated by 

 a knife in homicidal wounds. The shape and position 

 of the bone have also been altered by pressure, as 

 seen sometimes in artisans following employments re- 

 quiring instruments, etc., to be pressed against the 

 chest. 



Certain holes may appear in the middle of the 

 sternum, and through them mediastinal abscesses may 

 escape, and surface abscess pass deeply into the thorax. 

 In the case of E. Groux, the bone was separated verti- 

 cally into two parts. The gap could be opened by 

 muscular effort, and the heart exposed covered only 

 by the soft parts. The sternum has been trephined 

 for mediastinal abscess, and for paracentesis in peri- 

 cardia! effusion, and it has been proposed also to 

 ligature the innominate artery through a trephine 

 hole in the upper part of the bone. 



The ribs are placed so obliquely that the anterior 

 end of one rib is on a level with the posterior end of 

 a rib some way below it in numerical order. Thus 

 the first rib in front corresponds to the fourth rib 

 behind, the second to the sixth, the third to the 

 seventh, the fourth to the eighth, the fifth to the ninth, 



