THE HIP- JOINT. 1G3 



through winch pass the obturator internus muscle and the internal 

 pudic vessels and nerve. 



The puTjic articTilaticii;, or si/}}ij)Ji//sis pitdis, is the connection of the 

 pubic bones in front, and is effected by fibro-cartilagiuous plates and 

 ligaments. The adjacent surfaces of bone are each coated with car- 

 tilage, and to this is attached the fibro-cartilage which unites them. 

 The fihro-cartiJage is thicker and stronger in front than behind, and 

 generally contains a synovial cavity towards the upper and back part of 

 the joint. The ligaments are named anterior, 2Jostmor, siqmior, anct 

 inferior. The anterior pubic ligament consists of irregular fibres 

 passing obliquely across from bone to bone in front of the symphysis. 

 The superior and posterior ligaments consist of only a few fibres on 

 the upper and back part of the articulation. The inferior or subpubic 

 ligament, thick and triangular, is attached to the rami of the pubic 

 bones, giving smoothness and roundness to the subpubic angle, and 

 forming part of the outlet of the pelvis. 



The obturator membrane, or ligament, is a fibrous septum attached 

 to the border of the thyroid foramen, which it closes, except at the 

 upper and outer part of its circumference, where a small oval canal is Icit 

 for the obturator vessels and nerve. The membrane is fixed accurately 

 to the bony margin at the upper and outer sides of the foramen, and to 

 the posterior surface at the inner side. The obturator muscles are 

 attached to its surfaces. 



Hovements. — In ordinary circumstances there is very little movement allowed 

 between the bones of the pchas. In the erect posture the sacram is throuoi so 

 much backwards that none of the advantage of the kej^-stone of an arch is 

 obtained by the tapering- of its form from base to apex. It is only by the 

 sinuosities of its auricular sm-f aces that it dii-ectly presses on the hip-bones ; and 

 as the width of the bone rather dimiuishes at the upper or ligamentous part, the 

 principal strain is borne by the posterior sacro-iliac ligaments, from which the 

 sacrum is in great measiu'e suspended (see fig. 148). The space Avhich might be 

 gained by the small amount of movement which is allowed between the bones 

 of the pehis in the ordinary state is increased during ijai-tuiition in this way, 

 that the lower part of the sacmm being pressed backwards, the "wider part of 

 the wedge formed by this Ijone is forced farther between the ossa innominata, 

 so as to separate them to ii greater degree, and thus to increase the capacity 

 of the pelvis. During pregnancy, also, a slight amount of separation may occui" at 

 the symj^hysis jiubis from relaxation of the connecting i^aiiis. (See Wood, article 

 " Pelvis" in '"Cyclopajd. of Anat. and Physiol. ; '' Zaglas, in Monthly Joum. of 

 Med. Science, 1851 ; J. M. Dmican, in Dublin Quart. Jonrn. of Med. Science, 

 1854, and Edia. Med. Joum. 1855 ; Struthers, " Anat. Observ.'") 



ARTICULATIONS OP THE LOWER LIMB. 



THE HIP-JOINT. 



This is a large ball and socket joint, in which the globular head of 

 the femur is received into the acetabulum or cot3doid cavity of the 

 innominate bone. The articular surface of the acetabulum is formed 

 by a broad riband-shaped cartilage occupying the upper and outer part, 

 and folded round a depression which, extending from the notch, is 

 hollowed out in the bottom of the cavity, and is occupied by delicate 

 adipose tissue covered with synovial membrane, the so-called synovial 

 or Haversian gland. The articular surface of the femm- presents a 

 little beneath its centre a pit in which the round ligament is attached, 



M 2 



