OBLITERATION OF SUTURES IN SKULL 513 



function of the sutures is to produce new osseous tissue along 

 the margin of the skull bones for the sake of the enlarging of the 

 braincase. This function is continued as long as the brain- 

 case needs enlarging, i.e., as long as the brain increases in volume. 

 Summarizing, I think it is clear, that in apes the sutures com- 

 mence to obliterate as soon as the enlargement of the brain 

 has ceased. And in this respect there is a remarkable differ- 

 ence between man and apes. In the former the sutures often 

 persist a long time after the brain has ceased growing. 



We can now return to our starting point and consider the 

 question whether there is some relation between the normal 

 progress of suture-obliteration in apes and premature oblifera- 

 tion in man. There is no doubt about the fact that man stands 

 in nearer phylogenetical relation to the anthropoids than to any 

 other representative of the primate stem. Therefore, since, 

 as a rule, the sutures begin to disappear in apes shortly after 

 the brain is full-grown, which happens in youthful animals, 

 we have the right to conclude that the condition in man is 

 of a progressive nature. This condition, i.e., the persistence 

 of the sutures during a certain period of the adult state, must 

 be considered as a peculiarity acquired by man during the 

 earliest phase of his phylogenetic evolution. 



This conclusion gives rise to the following question. Should 

 not the premature obliteration of the sutures in the braincase 

 of man be considered an atavistic phenomenon? This hy- 

 pothesis deserves our full attention. If the statement is ac- 

 cepted as true, that in human ancestors the sutures closed as 

 those of the anthropoids of today, i.e., at an early stage of life, 

 then the occasional premature obliteration in recent man loses 

 its non-proved pathological character and becomes more in- 

 telligible. For we know that each quality newly acquired in 

 the evolution of beings often requires a long space of time be- 

 fore it becomes absolutely fixed. During this period the ante- 

 cedent condition reappears individually now and then. For my 

 part I think I may conclude that the premature closure of sutures 

 in infant-skulls is such an atavistic phenomenon. 



