9 OBSTETRICAL ANATOMV. 



foramina. The coccygeal bones are strong and tuberous, and the first 

 five or six are as perfect as the true vertebral bones. 



Pig. 



The pelvis of the Pig resembles that of the Sheep. The crest of the 

 iliiwi is convex, and there is no external protuberance on the symphysis 

 pubis. The jiubis is narrovs^; and the ischiuvi, instead of a crest, has a 

 tuberous prominence. The sacrum is formed by four vertebrae, w^hich 

 do not become fully consolidated for a long time, and it is sometimes 

 difficult to discover w^here the sacrum ends and the coccyx begins. The 

 spinous processes are absent ; and the neural arch being deficient on 

 each side, the spinal canal is open above. There is nothing particular 

 to note in the coccygeal bones. 



SECTION II.— ARTICULATIONS OF THE PELVIS. 



The bones of the pelvis are united by articulations and ligaments? 

 as well as fibrous bands, which are complementary. A knowledge of 

 these is of some importance to the obstetrist. The articulations are 



Fig. A. 



Lateral Ligaments of the Sacrum and Pelvis. 



a, Superior Sacro-iliac Ligament ; h, Sacral Ligament ; c, Lateral Sacro-iliac 

 Ligament ; d, Sacro-sciatic Ligament ; e, Small Sciatic Notch ; /, Great 

 Sciatic Notch. 



five in number : (1) the mcro-lumhar, (2, 3) the two sacro-iliac, (4) the 

 ischio-pubic symphysis, and (5) the sacro-coccygeal articulations. The 

 ilio-sacral and sacro-sciatic hgaments complete the subject of this 

 section. 



1. Sacro-lumbar Articulation. 



The sacro-lumbar articulation is formed between the anterior face or 

 base of the sacrum, and the last lumbar vertebra; the union takes 

 place by five articular surfaces and thick fibro-cartilages, and numerous 

 strong hgaments bind the two bones closely and very firmly together, 

 so as to allow only a very restricted amount of movement between them. 

 It would appear that these bones, though so hmited in their movements 

 on each other, yet are never anchylosed in old age nor yet by accident, 

 even if all the other vertebrye in this region should happen to be con- 

 solidated. 



