1042 EVOLUTIONAL MODIFICATIONS 



real changes ascribed to diseases of the pineal gland, particularly in the 

 early years of adolescence, producing the condition known as macrogenito- 

 somia praecox or the syndrome of Pellezzi. Under these conditions the 

 individual grows prematurely tall with precocious sexual differentiation. It 

 is the belief that the pineal gland normally holds in abeyance the premature 

 development of the statural and sexual organization by exerting upon the 

 pituitary body an inhibitory influence. Whether these potent factors in control 

 of the metabolic mechanism entered into the causes which produced the 

 critical change in body modification must still be a matter for further investi- 

 gation. They offer a most enticing suggestiveness. Either they or other similar 

 factors bore some responsibility in these epoch-making changes. In any case, 

 it must have been the near approach to the ground and the final necessity of 

 living upon it which determined the specialization leading to the development 

 of the human foot. At that juncture the embarrassment of over-endowment 

 arising from too much in the way of manual specialization began to dissipate 

 its restrictive influence. With the critical differentiation of the lower extrem- 

 ity in process, with the upright position guaranteed, with the final 

 emancipation of the hand a certainty, the ultimate instrument for extending 

 the boundaries of the neokinetic sphere was at length assured. Too niueh 

 emphasis cannot be laid upon this decisive change in the two branches of the 

 orthograde division of the primate stem. In consequence of it, the members 

 of one branch retained so much of their arboreal specialization that they 

 continued to be occupants of the forest. Quite the contrary is true of that 

 branch which finally began to stand upright and go upon two feet. Through 

 it, the neopallium now proceeded to externalize all of those potential resources 

 which had so long been held in reserve awaiting the arrival of tliis ultimate 

 manual equipment. From Pithecantluopus and the Dawn man, from Heidel- 

 berg man and the Neanderthal, through all of the achievements of Homo 

 sapiens, the human race has set the full imprint of man's past and contem- 



