THE BUILDING OF REFLEX ARCS 235 



regions of structural and functional change and became increasingly 

 dominant over his environment. Changes in muscles, joints, 

 bones, bursse, lungs, heart, and vessels occurred through his employ- 

 ing in new modes the muscles, joints, bones, bursse, lungs, heart 

 and vessels he already possessed, and the resemblance between 

 these structures of man and the great apes has given to the latter 

 the name of anthropoid, and this similarity of structures in the 

 highest Primates has done much to support in the past that Simian 

 origin of man which is at present questioned. The behaviour of 

 the apes and early man were sufficiently alike to lead either to 

 a parallel or genetic similarity. This point is, perhaps, irrelevant 

 in considering the great field for initiative in the formation of new 

 physical characters, and chief among these new reflex -arcs which 

 have built up the marvellous organ of man's glory and greatness ; 

 but no one can dispute the elementary fact that the ancestor of 

 man who adopted terrestrial bipedal locomotion and became 

 orthograde, owed it to his growing brain and the higher integration 

 of his organs for that function. But besides the new posture he 

 had adopted he learned to talk articulately, to make tools, and to 

 use stereoscopic vision. None of these could have been started 

 on the upward way without a long process of trial and error in the 

 course of his total experience and practice of his powers. The 

 results that followed from these three properties of his are in- 

 conceivably great, and it is unnecessary to enlarge on such a theme 

 or to add to the number of examples. 



Leaving, then, the immediate ancestor to work out his own 

 destiny in his new terrestrial home, we must as before proceed 

 backward in the history of animal life in the line of Primate ancestry. 



Primate Ancestry. 



It is generally agreed to trace the Primates back to an active 

 pioneer animal form which took to the trees, and which arose out 

 of the widely-spread Insectivores. This derivation will probably 

 satisfy any reasonable genealogist. But, if we may use a parallel 

 in human families, this active animal was as different from its 

 congeners as Napoleon was from his four brothers who played a 

 part in European history, and it is not necessary to say more as to 

 the significance of this fact than that the relative importance of 

 c; chassis " and ' ; body " is again a useful analogy. But we need to 

 ask what those congeners did if we are to succeed in understanding 

 the Napoleon-like course of him who became our Primate ancestor. 

 From the original widely-spread and plastic raw material of the 

 Insectivores allied forms took different lines, and their stories are 



