THE BONES OF THE LOWER LIMB 277 



The posterior extremity of the foot is formed by the tuber calcis. 

 Posteriorly this tuberosity presents three transverse zones — -upper, 

 for a synovial bursa ; middle, for the insertion of the tendo Achillis ; 

 and lower, for the fat of the heel. 



The posterior border of the astragalus, though it stops short of the 

 posterior extremity of the foot, may be referred to. The markings 

 which it presents are a groove and two tubercles. The groove, 

 which is directed downwards and inwards, transmits the tendon of 

 the flexor longus hallucis, and leads to the groove on the under 

 aspect of the sustentaculum tali of the os calcis. The external 

 tubercle, of large size, gives attachment superiorly to the posterior 

 fasciculus of the external lateral Ugament of the ankle-joint. The 

 internal tubercle, which is small, gives attachment internally to a 

 few fibres of the internal lateral or deltoid ligament of the ankle- 

 joint. 



The sinus tarsi or astragalo-calcaneal canal is the obhque tunnel 

 which Ues between the astragalus and the os calcis. Its direction 

 is outwards and forwards, and it is occupied by a strong inter- 

 osseous ligament, within which is the bursa sinus tarsi. 



For the Arches of the Foot, see p. 577. 



APPROXIMATE HOMOLOGIES OF THE BONES OF THE LIMBS. 



Upper Limb. Lower Limb. 



I. Shoulder Girdle and Pelvic Girdle. 



Scapula - - - =r Ilium. 



Coracoid - - - — Ischium. 



Precoracoid of mono- ^ _ n w 



tremata and reptUes ) ~ us pubis 



Clavicle ... Absent. 



(If, however, the clavicle is the morphological representative of the pre- 

 coracoid of monotremata and reptiles, then it is homologous with the os pubis.) 



Upper Limb. Lower Limb. 



Special Homologies of Scapula and Ilium (Flower). 



Scapula. Ilium. 



Inferior angle - - = Anterior superior spine. 



Superior angle - - = Posterior superior spine. 



Base - - . - = Crest. 



Axillary border - - - Anterior border. 



Superior border - - = Posterior border. 



Supraspinous fossa - = Sacral surface. 



Infraspinous fossa - = Iliac fossa. 



Spine and acromion - = Ilio-pectineal line. 



Subscapular fossa - = Gluteal surface (dorsum ilii). 



Glenoid cavity - - = Cotyloid cavity. 



