ANIMAL LOCOMOTION. 93 



which pass from tlie trunk to the limbs. The reflections of light 

 from the hair of the figures of the horse may be ascribed to the 

 changes in degrees of convexity or concavity of the superficial 

 muscle-masses, while some of the stripes of the tiger, especially 

 those of the fore limb and the neck, will be found to answer 

 to the depressions existing between well-defined positions of 

 muscles which can be named with accuracy. In the figures of the 

 roan horse (series 582) the black patch on the rump corresponds 

 to the great biceps muscle. 



In the horse (series 579) the depressions between the muscles 

 of the posterior aspect of the thigh are most marked when the 

 limb is in the first stage of the recover, but are obliterated when 

 the limb is in backward strain. The niasses at the inner border of 

 the thigh, as seen in the horse (series 582), are nearly flat when 

 the limb is off the ground, but conspicuously convex when the 

 animal is using the limb for support. 



In the dog, M'hen both fore feet are off the ground, the muscles 

 which pass from the trunk to the fore limbs are exceedingly 

 tense. 



On the Significance of the Skin-Folds on the Trunk of the Hog. 



A number of minute changes in the contour of the animals are 

 worth noting. In the figures of the hog (series 673 to 675), at the 

 time when the limbs of a single side are the nearest one to the 

 other the skin is observed to be thrown into a series of vertical 

 folds. It is suggestive of the mechanical origin of the bands in 

 the armadillo that the lines in the hog are in the same position 

 as the bands. They appear to differ only in the circumstance 

 that the folds are transient, while the bands are permanent. (See 

 p. 45.) 



The Mane. 



Each time the horse, in the series 590, leaves the ground by one 

 of the hind feet the mane streams backward. In series 638, as 

 the animal descends the mane streams upward. This change in 

 position is caused by the motions of the head and neck upward 

 and downward. (See especially figures of the horse rocking, series 

 649 A. See p. 48.) 



