240 



COMPARATIVE ANATOMY 



the precoracoid, remnants of which, however, usually occur within the 

 clavicle. See Fig. 196. 



-+-01V10STERNUM 



SUPRASCAPULAi 

 SCAPULA' 



CLAVICLEv 



EPIPHYSIS 

 OF CLAVICLEi 



INTER- 

 CLAVICULAR 

 LIGAMENT 



Fig. 196. — Diagrams illustrating the fundamental similarity of the human (B) and 

 amphibian (A) pectoral girdle. In man the coracoid element has degenerated into a 

 process (coracoid) and a connective tissue ligament containing occasional cartilage 

 nodules. (Redrawn after Huntington.) 



The mammalian hip bone differs little from that of reptiles. The 

 number of sacral vertebrae to which the coxal bone is attached increases in 



_UO-PUBOIsaflADtC CAflT, , _ 



ILIO-PUBO-ISCHAOtC CAfiTIUAO€_ 



D.NECTUBUS. E. OACTYLETHRA T CHELYDRA. 



Pig. 197. — A series of six appendicular skeletons illustrating the gradual emergence 

 of the elements of the pelvic girdle found in reptiles and mammals. They probably 

 represent fairly well stages in the evolution of the human pelvis. First came the separa- 

 tion of girdle and extremity {A and B) ; then the fusion of the paired elements of the 

 girdle into a median ventral cartilaginous plate (C and D) ; the difTerentiation of bony 

 ischium, pubis, and ilium (D and E); and finally the appearance of the obturator 

 foramen (F). There is no essential difference between the reptile and mammal girdle. 

 (Redrawn after Wilder, "History of the Human Body"; Henry Holt & Co.) 



mammals. In man there are five sacral vertebrae, to three of which the 

 hip bone is attached. 



