106 ARBOREAL MAN 



limbed Reptiles; the same type of movement, Ave may 

 fairly hazard, was characteristic of the extinct gigantic 

 forms of which the bony evidences of the mechanism are 

 so clearly preserved. 



Among the plastic Mammals, the evidence of function 

 is very easily seen. Animals which hop, jump, spring, 

 leap, or gallop show the presence of well-marked paite^ 

 version and retroversion of the spinous processes. Nearly 

 all Rodents and Insect ivores possess this feature. Of 

 the Carnivora, the cats which spring, and the dogs which 

 leap and gallojD, have a strongly divided series of spinous 

 processes, while the shuffling bears show a vertebral 

 column of which all the spines anterior to the sacrum 

 are directed backwards. Leaping and galloping LTngu- 

 lates, which can use both fore-limbs and both hind-limbs 

 alternately in their full stride, provide the classical 

 example of the anticlinal spinous process at the pen- 

 ultimate rib-bearing vertebra. Some very striking ex- 

 ceptions are worth noticing among the Ungulates. We 

 have already called attention to the curious gait of the 

 Giraffe, which in quiet progression advances both limbs 

 of the same side at the same time. It is interesting to 

 find that in this animal all the cervical, dorsal, and lumbar 

 spinous processes slope backwards — there is no centre 

 of movement until the region of the hips is reached. I 

 should imagine that, even when hard pressed, a Giraffe 

 cannot break into a gallop, and that it possesses little or 

 no power of jumping, but I know of no authoritative 

 observations upon these points. The spinous processes 

 of Okapia are arranged upon the same simple plan, and 

 I presume that it possesses the same peculiar gait, and 

 the same probable limitations of activity as the Giraffe. 

 It is not surprising that the lumbering Elephant, with 

 its peculiarly rigid backbone, should have no dorsal 

 centre of movement, and no anticlinal vertebra, and the 

 same feature is shared by such simple paddlers as the 

 Sirenia. 



