Chap. 7.] Hip Bones. uy 



concave in its broadeft fore part, whence a fmall finuo- 

 fity is continued obliquely forwards, at.the infide of the 

 anterior fpinous proc<?fs. This ridge is continued from 

 the os facrum, and correfponds with a fimilar* promi- 

 nence, both of that bone and of the ifchium, and forms, 

 with the inner part of the os pubis, what is called the 

 brim of the pelvis. The posterior and lower parts o,f 

 ihe ofTa ileum are thick ; but at their middle, where 

 they are expofed to the actions of feveral ftrong mufcles, 

 and to the preffure of the abdominal vifcera, they are 

 exceedingly thin and compacT. 



The offa ifchii or |iip bones, form the lower and 

 lateral parts of the pelvis : each is commonly divided 

 into its body, tuberofity and ramus. From the body 

 of the ifchiurn the fharp fpinous procefs Hands out 

 backwards,, to which the anterior or internal facrofcia- 

 tic ligament is fixed. Between the upper part of the 

 ligament and the bones, it was formerly obfcrved that 

 the fciatic nerve, &c. pafs out of the pelvis. The tu- 

 berofity, or lowed part of the ifchium, is large and 

 irregular, affords an origin to feveral mufcles, and is 

 the part on which the body refts in the pofture of fit- 

 ting. From die tuberofity the bone becomes thinner 

 and narrower ; and pafllng forwards and upwards, con- 

 curs with the ramus of the os pubis, to form a large 

 hole, called the' foramen magnum iichii, or thyroicleum. 

 This hole, which in the recent lubjeft is clofed with 

 a ftrong membrane, called the obturator ligamenr, 

 affords through its whole circumference attachment to 

 mufcles. 



The offa pubis confdtute the anterior, or, when the 

 body is ered, the lower part of the pelvis. They are 

 of an irregular form, and as well as tne other parts of 

 the offa innominata have a fhare in forming the aceta- 

 bulum. The two offa pubis are joined ^ogether by 

 I 3 - cartilage 



