THE SKIN AND SKELETON. 145 
(as in Birds) with the fibula also. An extra bone, the 
patella, or knee-pan, is hung by a muscle in front of the 
joint between the femur and tibia of the higher animals. 
The foot is made up of the. tarsus, or ankle; the meta- 
tursus, or lower instep; and the phalanges, or toes. The 
toes number from 1 in the Horse to 5 in Man. 
Certain parts of the skeleton, as of the skull, are firm- 
ly joined together by zigzag edges or by overlapping; in 
either case the joint is called a suture. But the great 
majority of the bones are intended to move one upon 
another. The vertebre are locked together by their 
processes, and also by a tough fibrous substance between 
the centra, so that a slight motion only is allowed. The 
limbs furnish the best examples of movable articulations, 
as the ball-and-socket joint at the shoulder, and the hinge- 
joint at the elbow. The bones are held together by liga- 
ments, and, to prevent friction, the extremities are cover- 
ed with cartilage, which is constantly lubricated with an 
unctuous fluid called synovza. 
CHEMICAL COMPOSITION OF BONES. 
Cop. Tortoise.) Hawk. Man. 
Phosphate of Lime, with trace of 
inate, Of LAME... svescecerscos code 57.29 52.66 64.39 59.63 
Carbonate of Lime..............0.00 4.90 12.53 7.03 7.33 
Phosphate of Magnesia............. 2.40 0.82 0.94 1.32 
Sulphate, Carbonate, and Chlorate 
OMSUU As ser aceaieccvasssevcecseosess 1.10 0.90 0.92 0.69 
Glutine and Chondrine............. 32.31 $1.75 | 25.73 29.70 
Sinn, makes WN cRepecavses stahessxescysds 2.00 1.34 0.99 1.33 
100.00 | 100.00 | 100.00 | 100,00 
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