536 



AMPHIBIA. 



The pelvic girdle has a long V-shape, the ends of which 

 are cartilaginous and articulate with the expanded trans- 

 verse processes of the ninth or sacral vertebra. Each 

 limb of the V is an ilium ; the united posterior part 

 consists of a fused pair of ischia, and a ventral cartila- 

 ginous pubic portion. Ilia, ischium, and pubes unite in 

 bounding the deep socket or acetabulum with which the 

 femur articulates. 



The skeleton of the hind limb consists of a thigh bone or 

 femur, a lower leg formed from the united tibia and fibula, 

 an ankle region or tarsus including two long proximal 

 elements — the astragalus or tibiale and the calcaneum or 

 fibulare — and two imperfectly ossified distal elements, five 

 metatarsal bones, and five toes. The first toe or hallux 

 has two phalanges, the second also two, the third three, 

 the fourth four, the fifth three, and, finally, outside the 



Fig. 178. —Side view of frog's Pelvis. (After Ecker.) 

 //, ilium ; Is, ischium ; Pb, pubis ; Ac, acetabulum. 



hallux there is a "calcar," which looks like an extra toe 

 and consists of three pieces. The astragalus is in line with 

 the first toe. 



Muscular System. 



I shall not describe the musculature of any of the 

 V ertebrate types With the guides to practical work cited 

 in the appendix the student will readily find out what he 

 wishes to know. 



The muscles are enswathed in connective tissue. They 

 consist of bundles of muscle fibres, and at their ends or at 

 one of them they are usually continued into strong tendons, 

 which are more or less directly attached to parts of the 

 skeleton. 



