20 SKELETON Of UPPER LIMBS. 



you cannot, although egg-shell is thin and brittle. The 

 bones on the sides and top of the brain-case are made 

 up of three layers: an outer, tough and fitted to bear 

 without breaking, blows from a heavy blunt object. Then 

 comes a much softer layer which deadens any jar that 

 might result from a blow on the head, and hinders its 

 transmission to the brain. Inside is a layer of very hard 

 bony matter, almost like glass, and admirably fitted to 

 stop or turn aside any pointed instrument which might 

 have penetrated the outer layers. If you turned upside- 

 down a thin china teacup, wrapped around it a covering of 

 raw cotton, and over this put a thin casing of tough wood, 

 anything placed under the cup would be protected from 

 blows, jars, and piercing, much as your brain is protect- 

 ed inside the skull. 



13. The Skeleton of each Upper Limb contains thirty 

 bones and is attached to the trunk by the shoulder-girdle. 



14. The Shoulder- Girdle presents on each side a collar- 

 bone or clavicle, in front (u, Fig. 3, and c, Fig. 5), and a 

 shoulder-blade or scapula (/", Fig. 5), behind. The collar- 

 bone and shoulder-blade unite near the shoulder-joint. 



15. The Bones of the Arm and Hand (Fig. 3) are: 

 (i) the arm-bone, or humerus, t, which reaches from the 

 shoulder to the elbow; (2) two forearm-bones lying side 

 by side between the elbow and the wrist; the one on 

 the thumb-side is the radius, g, and that on the little- 

 finger side the ulna, f; (3) twenty-seven hand-bones. 



13. How many bones in the forelimb? How is it attached to the 

 trunk ? 



14. What bone forms the front part of the shoulder-girdle ? Be- 

 hind ? Where do these bones unite ? 



15. Name the bones of the arm. Give position of humerus. 

 Radius. Ulna. Carpal bones. Metacarpal. Phalanges. 



