20 



THE SKELETON OF THE C/iT. 



Fig. i6. — Ster- 

 num, Ventral 

 View. 



a, manubrium; 

 b, the separate 

 pieces forming 

 the body ; c, bony 

 part of the xi- 

 phoid process 

 (the expanded 

 cartilaginous por- 

 tion not being 

 shown) ; d, facet 

 for attachment of 

 first rib. 



III. STERNUM. (Fig. i6.) 



The sternum consists of three portions, a 

 cranial piece or manubrium [a), a caudal piece 

 or xiphoid process (r), and a middle portion or 

 body (corpus), which is divided into a number 

 of segments (/;). 



To the sternum are united the ventral ends 

 of the first nine ribs. It thus forms the median 

 ventral boundary of the thorax. Since the 

 thorax decreases in dorsoventral measurement 

 craniad, the long axis of the sternum is incliifed 

 from its caudal end dorsocraniad, and if con- 

 tinued would strike the vertebral column in the 

 region of the first cervical vertebra. 



The manubrium {ex) makes up about one-fifth 

 the whole length of the sternum and projects 

 craniad of the first rib. It has the form of a 

 dagger and presents a dorsal surface and two 

 lateral surfaces, the latter uniting ventrad to 

 form a sharp angle. In the middle of the lateral 

 surface near the dorsal margin is an oval articu- 

 lar surface {d) borne on a triangular projection. 

 It looks caudodorsad and is for the first costal 

 cartilage. 



The caudal end articulates with the body by 

 a synchondrosis and presents a slightly marked 

 oval facet on each side for the second costal 

 cartilage. 



The body consists of six cylindrical pieces {b) 

 enlarged at their ends and movably united by 

 synchondroses. They increase in breadth from 

 the first, and decrease slightly in length and 

 thickness. At the caudal end of each near its 

 ventral border there is a pair of facets looking 

 caudolaterad. They are for the costal carti- 

 lages. 



The xiphoid process [c) is a broad thin plate 

 of cartilage at its caudal end ; bony and cylin- 



