102 SKELETON. 



under the anterior ridge of the pubes. It conducts the obtura- 

 tor vessels and nerve to the inner side of the thigh. 



The texture of the os innominatum is cellular internally, 

 with a condensed lamella externally. It is of very various 

 thickness. The ilium, in its centre, has the external and 

 internal sides so near one another, that in most adults the light 

 will shine through it. A large foramen is seen on the venter 

 of the ilium, and another on its dorsum, for the transmission of 

 nutritious arteries. There are several others, smaller, at va- 

 rious points of the os innominatum, for the same purpose, and 

 for the adhesion of ligamentous fibres. 



SECT. V. OF THE PELVIS, GENERALLY. 



The sacrum and coccyx behind, and the ossa innominata at 

 the sides and in front, constitute, as observed, the whole cavity 

 called pelvis, (bassin.) Its position is such, that, in the adult, 

 it divides the entire length of the body into two parts nearly 

 equal, the head and trunk forming one part, and the lower ex- 

 tremities the other. Generally, the former are somewhat the 

 longest ; but in cases of unusual corporeal stature, the excess 

 depends upon an undue length of the inferior extremities. On 

 the contrary, in persons of little height, the latter have not been 

 developed in proportion to the trunk of the body. 



The pelvis, as a whole, is a conoidal cavity, having its base 

 upwards, and the summit below. Its internal surface forms an 

 irregular floor, on which the viscera of the abdomen are sus- 

 tained in the erect position; and its external surface, by pro- 

 jecting considerably at various places, establishes very favour- 

 able points for the origin of muscles. 



The internal surface of the pelvis is divided by the projection 

 of the anterior margin of the base of the sacrum, and by the li- 

 nea ilio-pectinea, into two cavities; the upper one is the great 

 pelvis, and the lower one, the little pelvis. The great pelvis is 

 the base of the cone, and presents at its anterior part a large de- 

 ficiency, which is supplied in the fresh subject by the abdominal 

 muscles. The little pelvis is a complete bony canal, much 

 deeper behind and at the sides, than in front. Its depth, behind, 

 is formed by the whole length of the sacrum and coccyx ; at the 



