172 



PELVIS. 



directed outwards, the knee always bent, and 

 the body trailing. They walk on the fore and 

 hinder legs alternately, and leap by a sudden 

 flexion of the body. 



The pelvis of the Anourous Batrachia is 

 interesting from the changes which affect it, 

 in their transition from the ichthycic to the 

 quadrupedal condition. 



The sacrum of the Frog (Jig. 1 1 1 . A and B) 

 is considered by Duges to be formed by 

 the last dorsal vertebra, which closely re- 

 sembles the preceding ones, except in having 

 very long and strong transverse processes (e), 

 to the tips of which the ilia are moveably arti- 

 culated. In the Rana pipa and Toad, how- 

 ever, the sacrum presents evident indications 

 of a "division into two vertebrae, there being 

 on each side a foramen for nerves, with two 

 prismatic and very rough transverse pro- 

 cesses. The coccyx of the Frog is composed 

 of two pieces (/), which, in the adult state, are 

 ankylosed together and to the sacrum, and 

 considered by some to form part of that bone. 

 They are formed, respectively, from three 

 points of ossification. In addition to these 

 there is a long cylindrical terminal spinous or 

 btyloid process (g), which is formed by a single 

 separate ossific point, and becomes ankylosed 

 so the other part at the adult period. This is 

 tonsidered by some to be a second sacrum, 

 end by others a coccyx. It has been supposed 

 ay Duges to cause, by its progressive ossific 

 development, the mortification and dropping 

 off of the tail at the period of transition from 

 the tadpole condition, and thus closing up 

 the spinal canal posteriorly. 



Fig. 111. 



A, anterior view of the Frog's pelvis ; B, side view 

 of the same bones; c, pelvic bones and fins of 

 Trout. 



The ilia (b) are very long and cylindrical, and 

 directed back wards,becoming almost horizontal 

 in the Rana pipa. They suspend between them, 

 by their apices, the long transverse processes 

 and body of the sacrum, like the springs of a 



coach. At their opposite extremities tney are 

 ankylosed, not only with the ischia and pubes, 

 but with each other (If) ; and thus the acetabula, 

 of which they form the greatest portion, are 

 closely approximated, and the pelvic outlet 

 assumes a V shape with the base at the 

 sacrum and the angle at the coalesced ex- 

 tremities of the ilia. The pubes and ischia 

 of both sides are coalesced together in an 

 azygos osseous plate ;(c), with a central 

 rounded crest marking the position of the 

 symphysis (d), the pubes being the last to 

 ossify. There is no foramen obturatorium. 

 The posterior outlet of the Frog's pelvis looks 

 almost directly upwards, and the anus opens, 

 at the extremity of the coccygeal spine, upon 

 the dorsal aspect of the animal. 



In the immature Batrachian a triangular- 

 shaped cartilage intervenes between the op- 

 posing ilia and the other pelvic bones in the 

 acetabula, which afterwards becomes oblite- 

 rated by the ankylosis of the bones. Duges 

 calls it an " os paracotyleal," analogous to the 

 " paraglenal" bone of the shoulder of the same 

 animal. There are also epiphysial pieces on 

 the ilia and ischia which represent the crest and 

 tuberosity of those bones respectively. 



The solidity and firmness of union of the 

 ischio-pubic portion of the pelvis in the frog 

 is a remarkable instance of modification and 

 adaptation of form to meet the requirements for 

 a strong and firm hold for the powerful triceps 

 cruris, external obturator, hamstring, and ad- 

 ductor muscles in the thigh of this animal. 

 The single pair of glutei also obtain an ex- 

 tensive attachment from the long ilia, and the 

 pyri/brmes from the long coccygeal spine, while 

 the strong abdominal muscles, acting on the 

 moveable ilia, give, as it were, an additional 

 segment to the hinder extremities. In this 

 manner the frog's pelvis is strikingly and di- 

 rectly adapted to its leaping progression. 



In the Fishes the pelvic structures dwindle 

 to elementary pieces, such as we have, men- 

 tioned in the bimanal and apodal Reptiles, 

 and finally disappear altogether. 



The pelvis is represented in these animals 

 by two bones, sometimes coalesced into an 

 azygos bone, which support the ventral fins. 

 In the Pisces thoracici these are suspended 

 by ligament to the coracoids, by which they 

 are advanced anterior to the pectoral fins, 

 and connected to the head ; but in the 

 Pisces abdominals they are detached from 

 the coracoids, and are suspended in the 

 muscles at the posterior part of the ab- 

 domen. t They are, however, subject to 

 great diversity of position. 



Owen considers the pelvic bones of fishes 

 to be the homologues of the pubes ; but, in the 

 opinion of Carus, they are to be considered as 

 ilia. Their inferior and ventral position, their 

 occasional union in a symphysis, their frequent 

 coalescence, and their attachment to the 

 generative organs, however, would support 

 rather the conclusion of Professor Owen ; the 

 support of the bones of the extremities not 

 being exclusively the iliac attribute, but also 



