70 



ORGANS OF SUPPORT, 



FIG. 34. 



body of each vertebra, so as to change their forms almost 

 to those of reptiles. A great portion of their vertebral 

 column, and of their os hyoides, and their branchial arches 

 become absorbed, their legs and arms become developed, 

 and many of the coccygeal vertebrae unite to form a single 

 piece ; so that these anurous highest kinds of amphibia 

 pass through the inferior forms of their class before arriving 

 at their perfect state. There are nine vertebrae in the frog 

 (Fig. 34.) the first of which (b,) has a double articular sur- 

 face, like two condy- 

 loid depressions for 

 the two prominent 

 condyles formed by the 

 body of the occipital 

 bone (a,) and this atlas 

 is without transverse 

 processes. The bodies 

 of the succeeding ver- 

 tebrae terminate pos- 

 teriorly by slightly con- 

 vex surfaces, and an- 

 teriorly by correspond- 

 ing depressions, and 

 the transverse pro- 

 cesses are long, but irregular in their forms and magnitude. 

 There are no ribs, and the pelvic arch is moveably connected 

 with the ends of the transverse processes of the last or 

 ninth vertebra (c, c.) This single vertebra forms, therefore, 

 a true sacrum, and the succeeding coccygeal vertebrae (d,) 

 are anchylosed into a single unperforated bone, slightly 

 grooved at its commencement, running along the dorsal 

 part of the pelvis, and entirely concealed within this part 

 of the trunk. The two iliac bones (e, e,) long, cylindrical, 

 and slightly curved, extend backwards from the sides of the 

 sacrum (c, c,) to the ossa ischii (f,) behind, and the small 

 pubic bones in front ; and these three bones, united by 

 sutures, form on each side of this compressed terminal 

 part (/,) of the pelvis, the cotyloid cavity for the reception 

 of the. head of the femur. The legs are here very large, 

 both for leaping and swimming. The long femur (/,) is suc- 

 ceeded by another long single bone (w, m,) the grooved 



