THE GIBBONS. I49 



embraces the smallest-sized, the slenderest-bodied, the longest- 

 limbed, and the most perfectly arboreal of all the Man-like 

 Apes. All are covered with thick woolly hair, which, on the 

 arms and fore-arms, converges (except in H. agilis) towards the 

 elbow. 



Their head is small and round, and the face compressed. 

 Except the Orangs, the Gibbons have the longest arms of all 

 the Apes, so long that when they stand erect the points of their 

 fingers can touch the ground. Compared with the spinal 

 column, their arms are as 19 to 11, while the legs are one-third 

 longer than it. The fore-arm is much longer than the arm 

 itself ; the hand is longer than the foot, and the thumb is very 

 long in proportion to the hand. The knee is free from the 

 side of the body, and the great-toe is well developed and 

 nearly one-half the length of the foot. The nails of both 

 the thumb and the great-toe are flat. Callosities, which are 

 wanting in all the other genera, are present in Hylobates, but 

 are very small. 



In the skull the occiput is convex ; the orbits are very large 

 and deep, and the supra-orbital ridges prominent. The 

 canine teeth are much larger than the others, and equally large 

 in both sexes. They are generally the last of the permanent 

 teeth to come in, but in the Gibbons they generally precede, 

 or are developed along with, the last molar. 



The vertebral column is nearly straight, presenting but little 

 of the spinal curvature seen in Man ; it has also in the dorso 

 lumbar region one vertebra more than in the human skeleton. 

 The articulating head of the arm-bone {Jiunierus) loses the 

 direction it had among the Monkeys, and looks upward and 

 forward as in Man. The wrist {carpus) has nine bones, as in 

 the lower Anthropoidea. The skeleton of the hand is more 



