676 MAMMALIAN ANATOMY 



To the outer surface of the body is attached the adductor longus, 

 and to the outer surface of the body and descending ramus are 

 attached the adductor brevis, the gracilis, and the obturator externus. 



The horizontal ramus joins the body with the ilium. Some ana- 

 tomical writers reverse these parts and call the body the horizontal 

 ramus, and vice versa. This ramus forms a fifth of the acetabulum. 

 On the inner surface, where it joins the ilium, is the ilio-pubic ridge, 

 the inner end of which forms the ilio-pectineal eminence and is con- 

 nected with the pubic spine by the continuation of the ilio-pectineal 

 line sometimes called the pectineal line. The pectineus muscle arises 

 in front of this line. The anterior border of the ramus from the spine 

 to the acetabulum is termed the obturator line, inasmuch as it limits 

 the area of origin of the obturator externus muscle. The obturator 

 foramen is irregularly oval in the male, and triangular in the female. 



THE PELVIS. 



General Description. The Pelvis is the bony framework 

 formed by the hip bones and the adjoining part of the vertebral 

 column ; it contains the posterior part of the alimentary and genito- 

 urinary tracts. It is something more than the pelvic girdles, for, in 

 addition to the innominate bones, it includes the sacrum and the 

 first four caudal vertebrae. The pelvic cavity is smaller than the 

 cranial and thoracic cavities, and its bony walls are stouter, but less 

 complete. It may be compared to a hollow cylinder whereof the 

 anterior end points upward and forward and the posterior end down- 

 ward and backward. 



The anterior ventral half of this imaginary cylinder is lacking, and 

 the dorsal wall is complete in front for only a short distance in the 

 region of the first sacral vertebra ; for most of its extent behind, it is 

 confined to a strip along the middle line formed by the second and 

 third sacral and the first four caudal vertebrae. The bones which form 

 the pelvis are all immovably united, except the four caudal vertebra^ 

 which are capable of free movement, not so free, however, as would 

 seem from the mounted skeleton, since the intervals between them and 

 the innominates are filled with muscles and ligaments. It will be 

 noticed that in the ordinary position of the cylinder-like pelvis the 

 immovable anterior part of the dorsal wall lies above the anterior 

 opening in the ventral wall, and the immovable posterior part of the 



