RIBS. TRUE AND FALSE. /3 



triangularis sterni, aponeurosis of the obliquus externus, internus, and 

 transversalis muscles, rectus, and diaphragm. 



RIBS. The ribs are twelve in number at each side ; the first seven 

 are connected with the sternum, and hence named sternal or true ribs; 

 the remaining five are the asternal or false ribs ; and the last two 

 shorter than the rest, and free at their extremities, are the floating ribs. 



Fig. 33." 



Q.8 / 



The ribs increase in length from the first to the eighth, whence they 

 again diminish to the twelfth; in breadth they diminish gradually 

 from the first to the last, and with the exception of the last two are 

 broader at the anterior than at the posterior end. The first rib is 

 horizontal in its direction ; all the rest are oblique, so that the ante- 

 rior extremity falls considerably below the posterior. Each rib pre- 

 sents an external and internal surface, a superior and inferior border, 



* An anterior view of the thorax. 1. The superior piece of the sternum 

 2. The middle piece. 3. The inferior piece, or ensiform cartilage. 4. The 

 first dorsal vertebra. 5. The last dorsal vertebra. 6. The first rib. 7. Its 

 head 8. Its neck, resting against the transverse process of the first dorsal 

 vertebra. 9. Its tubercle. 10. The seventh or last true rib. 11. The costal 

 cartilages of the true ribs. 12. The last two false ribs or floating ribs. 13. The 

 groove along the lower border of the rib. 



