46 ARBOREAL MAN 



most healthy tonic for the human comparative anatomist 

 as well as for the human philosopher ; in these two hypo- 

 thetical works there is no doubt that the human fore- 

 limb would suffer badly. Far from being regarded as 

 the acme of evolutionary processes, it would be judged 

 as an extraordinary survival of a very primitive feature 

 far into the mammalian series, and more would be written 

 upon its striking similarity to the corresponding member 

 in the salamander and the tortoise than of its adaptation 

 to the multitude of human functions. This is a silly 

 argument, and no comparative anatomist not resident 

 in the kingdom of the Houyhnhnms would enter into 

 discussion with a quadruped that wrote a thesis showing 

 that the human fore-limb was very like that of a water- 

 newt. I have, however, brought the subject forward in 

 this way of set purpose, for as unbiassed judges of our- 

 selves we are to say definitely one way or the other: 

 Is the arrangement of bones and muscles we have seen 

 in the human arm a gradually elaborated evolutionary 

 perfection, or is it merely the retention of a condition ; o 

 primitive that it is matched only among its immediate 

 kin, and by types situated in the vertebrate stock right 

 at the point of mammalian divergence ? In anatomical 

 terms we may say : Have we lost a primitive arrangement 

 of bones and muscles, and then regained them, in evolu- 

 tion, upon exactly the same lines, or have we simply 

 retained them comparatively unaltered from the dawn 

 of mammalian specialization ? We must not overlook 

 in this the gravity of the second alternative, for it carries 

 with it the assumption that the human stock began to 

 be differentiated in that dawn period when the Mammals 

 themselves were evolved from some possible Theromorph 

 ancestor. With all the evidence that is available I cannot 

 see how it is possible to avoid this second conclusion. 

 In bones, and in muscles, the human fore-limb is far 

 more like that of a tortoise than it is like that of a horse 

 or a dog. This is no fanciful way of stating the case, 



