208 



THE SKELETON 



the inner surface of the one comes to correspond with the outer surface of the other. It results 

 that the primitive vertebral surface of the scapula is now the pre-scapular or supraspinous 

 fossa, and the corresponding surface in the ilium is the sacral, which, on account of its close con- 

 nection with the vertebral column, undergoes but little change in position. Further, the primi- 

 tive pre-axial surfaces are the infraspinous fossa and the iliac fossa, which accordingly are to 

 be regarded as homologous, as well as the two post-axial surfaces, the subscapular fossa and the 

 dorsum iUi. The correspondence between the various parts of the scapula and ilium is shown 

 in the appended table (after Flower). 



I. Surfaces : 



II. Borders: 



Scapula 



Supraspinous fossa. 

 Infraspinous fossa. 

 Subscapular fossa. 

 Axillary or glenoid. 



Spine. 



Superior or coracoid. 



Base. 



Primitive 

 Arrangement 



Vertebral. 

 Pre-axial. 

 Post-axial. 

 External. 



Antero-internal. 

 Postero-internal. 

 Dorsal extremity. 



Ilium 



Sacral surface. 

 Iliac fossa. 

 Gluteal surface. 

 Cotyloid or anterior 



border. 

 Terminal line. 

 Posterior border. 

 Crest of ilium. 



II. Bones of the arm and thigh, forearm, and leg. — It has already been pointed out in 

 describing the deviation of the limbs from the primitive position that the humerus corresponds 

 to the femur, the radius to the tibia, and the ulna to the fibula; also that in consequence of the 

 rotation backward of the fore-limb, and forward of the hind-limb, the lateral side of the humerus 

 corresponds with the medial aide of the femur, the radial border of the forearm to the tibial 

 border of the leg, and the ulnar (border of the forearm) to the fibular border of the leg. The 

 corresponding parts are tabulated below: — 



Fore-Limb 

 Humerus 



Greater tuberosity 



Lesser tuberosity 



Lateral epicondyle and capitulum 



Medial epicondyle and trochlea 

 Radius 

 Uhia 

 Not represented 



Femur 



Hind-Limb 



Lesser Trochanter 

 Great Trochanter 

 Medial Condyle 

 Lateral Condyle 



Tibia 



Fibula 



Patella 



in. Bones of the hand and foot. — It is obvious that the carpus and tarsus, the meta- 

 carpus and metatarsus, and the various digits, commencing at the thumb, in the hand, and at 

 the great toe, in the foot, are serially homologous. 



Fig. 254. — Dorsal Surface of the Right Manus of a Water-tortoise, Chelydra serpentina. 



(After Gegenbaur.) 



In order to trace the correspondence between the various elements of the carpus and tarsus 

 it is convenient to refer in the first place to the primitive type of hand and foot as found in the 

 water- tortoise and the lizard (fig. 254). In each segment nine elements may be recognised, 

 arranged in a proximal row of three, named respectively radiate or tibiale, intermedium, and 

 ulnare, or fihulare, a distal row of five carpalia, or tarsaiia, numbered from one to five, commenc- 

 ing at the pro-axial border, and between the two rows an os centrale. 



In man the carpus i.s (lorivod from the typical form in the following manner: The radiale 

 forms the navicular, intorrnediuin the lunate, and the ulnare, the triquetral; carpale I forms 

 the greater multangular, carpale H the lesser multangular, carpale III the capitate, whilst car- 

 paUa IV and V coalesce to form the hamate. The os centrale is present in the human carpus 

 at an early stage, but in the .s(3Cond month it joins the navicular. It is occasionally separate — 

 a normal arrangement in most of the primates. 



