162 THE AR TICULA TIONS. 



Fixed by its adherent border to the margiii of the cotyloid cavity, this 

 ligament is lined by synovial membrane on its faces and free border. It is 

 thickest in front and within. 



With regard to the head of the femur, it will be remembered that it is 

 exactly moulded to the cavity, and, like it, is excavated by a rugged fossa 

 which is entirely occupied by the insertion of the interarticular ligaments. 



Mode of union. This joint is maintained by a peripheral capsule, and 

 by two interarticular bands constituting the coxo-femoral and pubio-femoral 

 ligaments. 



a. Capsular ligament (Fig 90, 4). This is a membranous sac, like that 

 of the scapulo-humeral articulation, embracing the head of the femur by its 

 inferior opening, and attached by its opposite aperture to the margin of the 

 cotyloid cavity and its protecting fibro-cartilage. This ligament is com- 

 posed of intercrossed fibres, and is strengthened in front by an oblique 

 fasciculus which descends to the body of the femur, along with the anterior 

 thin muscle, near which it is fixed. Its internal face is covered by the articular 

 synovial membrane, and its external face is in contact, through the medium 

 of adipose cushions, with : in front, the anterior thin muscle (crureus) and 

 the straight muscle (rectus) of the thigh ; behind, to the gemini, the internal 

 obturator, and the pyramidal muscles ; outwards and upwards, to the small 

 gluteal muscle ; within and below, to the external obturator. 



fe. Coxo-femoral ligament (ligamentum teres, Fig. 90, 6). A thick and 

 short funicle of a triangular shape, deeply situated between the two bony 

 surfaces, which it cannot, notwithstanding its shortness, maintain exactly in 

 contact without the other muscular or ligamentous structures enveloping the 

 articulation. Its upper insertion occupies the internal moiety of the bottom 

 of the cotyloid cavity ; and its inferior extremity is confounded with the 

 pubio-femoral ligament, being fixed with it into the rough fossa in the head 

 of the femur. It is enveloped by the synovial membrane. 



c. Pubio-femoral ligament (Fig. 90, 7, 8). This ligament, longer and 

 stronger than the last, originates from the pubic tendon of the abdominal 

 muscles and the anterior border of the pubis. Lodged in the inferior 

 channel of that bone, it passes outwards, enters the internal notch of the 

 cotyloid cavity, is inflected downwards on the fibrous band which converts 

 that notch into a foramen, and goes with the preceding ligament to be 

 inserted into the fossa in the head of the femur. Its pubic portion lies 

 between the two branches of the pectineus, while its interarticular surface 

 is covered by synovial membrane. 



Synovial membrane. This membrane is very extensive; it lines the 

 internal face of the capsular and cotyloid ligaments, and is reflected on the 

 interarticular ligaments to form around them a serous vaginal covering. It 

 is even prolonged into the synovial fossa occupying the centre of the cotyloid 

 cavity. 



Movements. The coxo-femoral articulation is one of the joints which is 

 endowed with the most varied and extensive movements. It permits the 

 flexion, extension, abduction, adduction, circumduction, and rotation of the thigh 

 on the pelvis. The mechanism of these movements is so simple, that they 

 need no particular consideration. 



The domesticated animals other than Solipeds, are distinguished by the complete absence 

 of the pubio-femoral ligament ; so that in them the movements of abduction, which are 

 limited in Solipeds by the tension of this ligament, are much more extensive; and it is 

 the absence of the ligament in question, which explains the facility with which the larger 

 Ruminanls are enabled to strike sideways, a movement known as a " cow's kick." 



