PELVIS. 



177 



These are represented in Man and Mam- 

 malia generally by the sacro-sciatic ligame?ifs, 

 and appear to be* ossified by extension from 

 the epiphysis of the ischiadic tuberosity, and 

 from the ischiadic spine. In Birds, they 

 constitute an important element of the 

 pelvis, and are separated, more or less, from 

 the ischium and sacrum by a faintly marked 

 suture, more evident, however, at the sacral 

 extremity. Taken in a scientific point of 

 view they represent two additional pelvic 

 rib shafts, or pleurapopkyses, of the two last 

 sacral vertebrae, and are implanted on the 

 sacrum, in the human pelvis, in the site of 

 the two lower lateral epiphjsial plates of that 

 bone, exactly as the ilia are articulated upon 

 the three upper. Their extension to the coccyx 

 would also seem to connect them with the 

 elements of the first coccygeal vertebrae ; 

 and their attachment to the ischia would be, 

 in this point of view, a repetition of the kind of 

 union of the latter bones with the descending 

 pubic rami, as the cartilages of the false ribs 

 are connected consecutively to each other in 

 the thorax. 



The obturator and sacro- sciatic foramina, 

 considered in this light, constitute simply 

 consecutive and enlarged intcrchondral and 

 intercostal spaces respectively ; the lesser sa- 

 cro-sciatic foramen becoming, in the Sloths, 

 Bats, and Birds, entirely obliterated. This 

 manner of viewing them explains the ap- 

 parently indifferent way in which the boun- 

 daries of these openings, especially the ob- 

 turator, are left incompleted, or entirely 

 obliterated, in Birds and Reptiles. The 

 cotyloid notch may be thus considered as the 

 commencement of the obturator separation, 

 and the formation of two obturator open- 

 ings, as in the Ostrich, may be readily ex- 

 plained. 



The obturator membrane may also be thus 

 related to the anterior intercostal aponeuroses^ 

 and the membranous expansion of the upper 

 border of the great sciatic ligaments (before 

 mentioned as connected with the fasciae cover- 

 ing the internal obturator and pyriformes mus- 

 cles), to the posterior intercostal ligaments. 



The homologues of the ligaments of the 

 sacro-iliac articulations are readily found in 

 those connecting the head, neck, and tubercles 

 of the thoracic ribs to the vertebra?. 



The anterior and superior sacro-iliac ligaments 

 are evidently repetitions of the anterior or stel- 

 late costo-vertebral ; the superficial fibres of the 

 posterior sacro-iliac, repetitions of the posterior 

 costo- transverse ; the deep fibres, or inter- 

 osseous sacro-iliac, of the middle or interosseous 

 costo-transverse ; and the ilio-lumbar and lumbo- 

 sacral ligaments, of the oblique or an'erior costo- 

 transverse ligaments of the ribs. The connec- 

 tion of the last-named ligament with the trans- 

 verse process of the vertebra above, and with 

 the iliac crest below, is very similar to the 

 oblique direction and attachments of the 

 homologous costo-transverse. The ossifica- 

 tion of these ligaments in Sloths, Bats, and 

 especially in Birds, gives additional support to 

 their otherwise feebly connected pelves. 



The ligaments of the pubic st/mpkysis find 

 Supp. 



easily their homologues in the chondro- sterna t 

 ligaments. The anterior and posterior peripheral 

 inter-pubic ligaments are repetitions of the 

 similarly placed and constituted chondro- 

 sternal, which, like them, connect the haema- 

 pophyses together across the interposed 

 elements, as well as directly to the endo- 

 sternal bones and inter-pubic fibre-cartilage. 

 The superior pubic ligament finds its homo- 

 logue in the inter-clavicular, and the sub~pubic t 

 in the chondro-xiphoid and interchondral fibres. 

 It would be easy also to point out the mus- 

 cular homologues of the two regions; but 

 space will not permit more than to mention 

 the evident ones of the external and internal 

 oblique muscles with the similarly placed and 

 directed intercostals ; of the levator ani with 

 the diaphragm ; and of the pyriformes with the 

 psoce muscles. The internal obturator muscles 

 would represent the triangularis sterni and 

 transversalis abdominis ; and the external, the 

 lesser pectoral and extei'nal oblique muscles. 



The homologues of the pelvic bones with 

 those of the shoulder are best seen in the Rep- 

 tiles. According to Duges, the pelvis of the 

 Salamander has a close resemblance to the 

 shoulder of the Cameleon. 



The ilium is generally considered to be the 

 homologue of the scapula ; the pubis, of the 

 clavicle ; and the isehium, of the coracoid bone. 

 Meckel considers the body of the ischium to 

 represent the spine of the scapula; while, in 

 the opinion of Oken, the pubis represents the 

 acromion process, and the marsupial bones the 

 clavicles. 



In the shoulder of the Cameleon, the sca- 

 pula is longer even than the ilium, and the 

 furcular clavicles and coracoids are ankylosed 

 together like the ischium and pubis. And, in 

 the pelvis of the Crocodile, we have seen that 

 the ischium excludes the pubis from the 

 formation of the acetabulum by an apophysis 

 which overhangs that cavity, somewhat as the 

 human coracoid process intervenes between 

 the glenoid cavity and the clavide. 



The ascending branch of the ischium may, 

 further, be taken to represent the epicoracoid 

 bones of the Monotremes, Lizards, Batrachians, 

 and some Fishes r as the Cod, Carp, and Perch, 

 In the Cock-fish, Snipe-fish, and Lancet-fish, 

 these bones are joined in a kind of symphysis, 

 forming an independent arch behind the sca- 

 pular arch. 



And those bones of the scapular arch o 

 the Fish, which are considered by Owen to be 

 the coracoids, (but by Meckel, Agassiz, Geof- 

 froy, and Spix to be clavicles,) unite also in a 

 median symphysis, presenting an homologous 

 affinity to the ischial symphysis seen in the 

 Reptiles, the whole of these symphysial ele- 

 ments being represented, combined, by the 

 elongated ischio-pubic symphysis in many 

 Mammalians, but especially in that of the 

 Marsupials and Monotremes. 



(John Wood.) 



BIBLIOGRAPHY. Descriptive Anatomy, by 

 Qiiain, CrtiveUiier, and Meckel. Ward, on the Bones. 

 E Ills' s Demonstrations. John James Watts, Ana- 

 tomico- Chirurgical View of the Male and Female 

 Pelvis. Encyclopedic Anatomique Jourdan's 



