SKELETON. 



55 



protect the carotid arteries. In the mammals they form the distal part of the 

 'transverse process' of human anatomy, the vertebrarterial canal and the develop- 

 ment revealing their true nature. 



The dorsal ribs are very short in amphibians, never extending far 

 from the backbone. They are bicipital in most forms, except the 

 anura where they form small projections on the ends of the transverse 



FIG. 53. Skeleton of trunk of common goose, Anser domesticus. c, cuneiform; ca, 

 carina; co, coracoid;/, furcula (clavicle) ; fe, femur; h, numerals; il, ilium; is, ischium; me, 

 metacarpals; p, pubis; ph, phalanges; r, radius; s, scaphoid; sc, scapula; sr, sternal rib; st, 

 sternum; u, uncinate process; id, ulna; vr, vertebral rib; 2, 3, 4, digits. 



processes. In the amphibia the vertebral artery is ventral to the par- 

 apophysis. In all other vertebrates with a sternum at least a part of the 

 dorsal ribs reach that structure, encircling the viscera like the hoops of a 

 barrel. Those ribs which do not reach the sternum are called false 

 ribs. In most reptiles and some birds most of the thoracic ribs bear an 

 uncinate process directed upward and backward (fig. 53), overlapping 



