THE LIMBS. 



299 



tive type of pelvic girdle, such as is seen in the crocodile or 

 lizard, and of which the mammalian type is a derivative, is 

 shown diagrammatically in Fig. 242. For comparison the human 

 girdle in a 5th week foetus is shown in Fig. 243. 



ventral median line 



acetabulum 



cost. proc. 



ischium 



jL cloaca 



Fig. 242. — Diagram of the Pelvic Girdle of a Lizard. 



The dorsal element consists of the ilium ; it is attached by 

 ligaments to the costal process of one or more sacral vertebrae. 

 In the ventral portion of the cartilaginous arch are developed two 

 elements, the pubes and ischium, both of which take part in the 

 formation of the acetabulum (Fig. 242). Both reach the ventral 

 median line in which cartilage is developed. 



1st sac. 



ant. crur. nerue 

 ubes 



median ventral line 

 obt. nerue 

 acetabulum 

 ischium 



—gr. sc. nerue 



coccyx 



Fig. 243. — The Pelvic Girdle of a Human Foetus at the 5th week. (After Kollmann ) 



In man the following changes may be noted: (1) The costal 

 processes of the sacral vertebrae (2 \ usually) have fused together 

 to form the lateral sacral mass, with these the ilium articulates ; 



