164: ANATOMICAL TECHNOLOOT. 



50). The ribs proper have each a general caudal inclination from 

 the tuberculum to the arthron costicartilaginis, while tlie carti- 

 lage has a cephalic inclination from the arthron to the sternal end 

 (Fig. 30). In full insi^u-ation the ventral or sternal ends of the ribs 

 are nearly ventrad of the vertebral ends, the caudal convexity being 

 partly or entkely obliterated (Fig. 50). 



§ 429. Special Characters. — The capitellum of the 12th and 

 13th ribs — 14th if present — articulates with but a single vertebra. 



The capitellum of the first articulates to a slight extent with the 

 body of the last cervical, but the diarthrodial part of the articula- 

 tion is entirely confined to the body of the first thoracic (Flower, 

 A, 23). The first rib and those last named above (12, 13, 14), pos- 

 sess no ligamentiim inter articular e (Fig. 50). 



The 12th and 13th ribs — 14th if present — possess no arthral 

 tuberculum ; it is also sometimes absent from the 11th. The tuber- 

 culum of each of the others articulates diarthrodially with the 

 diaphysis of the vertebra corresponding to it in number ; thus, the 

 tuberculum of the first articulates with the diapophysis of the first 

 vertebra, and that of the seventh with the diapophysis of the sev- 

 enth, etc. 



§ 430. Sternal, Asternal and Floating Ribs. — The cartilages of 

 the first nine ribs (Fig. 49)— rarely of only the first eight — are articu- 

 lated with the sternum , and hence are called sternal or true ribs. The 

 remaining three (or four) are called asternal or false ribs, as their 

 cartilages do not reach the sternum. Finally the 13th — 14th if pres- 

 ent — is not attached to the one just cephalad of it by connective 

 tissue, as are the 10th, 11th and 12th, but ends independently in 

 the abdominal muscles, and hence is called a floating or vertebral 

 rib. (Humphrey, A, 329, 337 ; Hutchinson, A,* 101 6. 



§ 431. Methods of Demonstration. — The form and the various 

 parts of tlie ribs are best made out in those that have been com- 

 pletely deprived of their soft parts as directed iabove (§ 248). The 

 relations and mobility of the ribs singly and collectively, and their 

 arthra and ligaments, must be studied on fresh or alcoholic speci- 

 mens. 



§ 432. Elasticity and Mobility. — Take as lean a cat as possi- 

 ble, place it dorsicumbent, and, commencing at the ventrimeson, 

 remove the skin and muscles covering the sternum, and the ribs 

 with their cartilages of one side. Press upon the thorax, and the 

 elasticity of the ribs will be felt. Grasp the second mesosterneber 



