THE FOOT. TARSUS. 



211 



the cartilaginous rings, which, by the thickness on their out- 

 sides, make the cavities of the tibia more horizontal, by 

 raising their external side where the surface of the tibia slants 

 downwards. By these means the motions of this joint are 

 more equal and steady than otherwise they would have been. 

 The cartilages being capable of changing a little their situation, 

 contribute to the different motions and postures of the limb, and, 

 likewise, make the motions larger and quicker. 



The Foot. 



The foot is divided into the tarsus, metatarsus, and toes. 

 The sole of the foot is necessarily described as the inferior 

 part, and the side of the great toe as the internal. 



Tarsus. 



Fig. 47.* 



The tarsus consists of seven spongy 

 bones ; to wit, the astragalus, os calcis, 

 naviculare, cuboidcs, cuneiforme externum, 

 cuneiforme medium and cuneiforme inter- 

 num. 



The astragalus is the ujipermost of 

 these bones. The os calcis is below the 

 astragalus, and forms the heel. The os 

 naviculare is in the middle of the internal 

 sides of the tarsus. The os cuboidcs is the 

 most external of the row of four bones, at 

 its forepart. The os cuneiforme externum is 

 placed at the inside of the cuboid. The 

 cuneiforme medium is between the external 

 and internal cuneiforme bones ; and the 

 internal cuneiforme is at the internal side of 

 the foot. 



The upper part of the astragalus is formed 



* The dorsal surface of the left foot. 1. The astragalus ; its superior quadri- 

 lateral articular surface. 2. The anterior extremity of the astragalus, vviiich 

 articulates with (4.) the scaphoid bone. 3. The os calcis. 4. The scaphoid bone. 

 5, The internal cuneiform bone. G. The middle cuneiform bone. 7. The exter- 

 nal cuneiform bone. 8. The cuboid bone. 9. The metatarsal bones of the first 

 aDd. second toes, 10. The first phalanx of the great toe. 11. The s^erond pha- 

 lanx of th3 great toe. 12. The first phalanx of the second loe. 13. Its second 

 phalanx. 14. Its third phalanx. 



