The Frog — An Amphibious Vertebrate A?iimal 425 



scapula (Fig. 210). The glenoid fossa is the cavity with which the hu- 

 merus of the forelimb articulates. The radioulna of the forearm is a 

 fusion of radius and ulna bones. Contrast this with man (Fig. 229). 

 The wrist consists of six bones (car pals). The hand is supported by 

 five metacarpals. Distal to the hand are the bones of the digits or fingers 

 (phalanges). 



The pelvic girdle (Fig. 210) to which the hindlimbs are attached is 

 attached to the transverse processes of the ninth or sacral vertebra. The 

 girdle is composed of a pair of long ilium bones (plural ilia), a pair of 

 ischium bones, and a pair of pubis bones. These three pairs of bones 

 articulate so that a cavity is formed {acetabulum) with which the femur 

 of the hindlimb joins. The anterior part of the acetabulum is formed by 

 the ilium and the posterior by the ischium, while the ventral part is 

 formed by the cartilaginous pubis. The tibio fibula is a fusion of the 

 tibia and fibula bones. Contrast this with man (Fig. 229). The tarsals 

 (ankle bones) are arranged in two rows, the proximal one consisting of 

 long bones, the astragalus and calcaneum. Contrast this with man. The 

 distal row contains a series of smaller bones. Distal to this are the five 

 elongated metatarsals (foot). Of the five toes (digits or phalanges), the 

 first and second contain two phalanges each, the third and fifth, three 

 phalanges each, and the fourth, four. On the tibial side of the first toe 

 there is an additional or accessory digit called the calcar or prehallux. 

 There are no claws. 



Motion and Locomotion. — Well-developed and complex muscles are 

 present in the body, appendages, and head (Fig. 211). Minor muscles 

 move the lower jaw, aid in breathing, pump blood, secure foods, eliminate 

 wastes, and produce sounds by means of the vocal apparatus. The mus- 

 cles attached to the skeleton are called skeletal muscles. Each has an 

 origin which is the more fixed end and an insertion which is the more 

 movable end. Pulsating lymph ''hearts" (two near the third vertebra and 

 two near the end of the vertebral column) force lymph into the trans- 

 verse iliac and internal jugular veins. 



Ingestion and Digestion. — Living insects, worms, and similar organ- 

 isms are captured by a rather sticky, extensile tongue attached at its 

 front end (Figs. 212 and 213). The tongue is thrown forcibly forward 

 by the rapid filHng of a lymph space beneath it. The large mouth cavity 

 bears cone-shaped teeth on the upper jaw. The two vomer bones in the 

 roof of the mouth bear vomerine teeth. A constricted, horizontal slit 

 separates the mouth cavity from the esophagus. The stomach is crescent 



