ON METOPISM 



L. BOLK 



Director of the Anatomical Institute, University of Amsterdam 



NINE FIGURES 



It is a well-known fact that in man the two frontal bones 

 in a certain number of individuals do not coalesce. In normal 

 circumstances the frontal or metopical suture begins to disap- 

 pear during the last quarter of the first year, and is completely 

 closed before the end of the second year, the anterior fontanelle 

 disappearing during the third year. The phenomenon of a 

 persisting frontal suture generally is designed as metopism. 



Many publications on metopism are contained in the anthro- 

 pological and anatomical literature. Several reasons have in- 

 duced me to add the present paper to them. Firstly, I am able 

 to deal with data unknown till now regarding the numerical oc- 

 currence of the phenomenon in Dutch skulls. Such a communi- 

 cation is not wholly superfluous because the frequency of metop- 

 ism varies not inconsiderably among different peoples or races. 

 The second reason for the publication of this paper is given by 

 the fact that in many points the results of my investigations con- 

 tradict those of other investigators, and, as to the etiology of the 

 phenomenon, I differ from the current opinion. Commonly an 

 increased intracranial pressure, caused by the somewhat more 

 strongly developing frontal brain, is regarded as the mechanical 

 factor preventing the fusion of the two frontal bones. So Martin 

 in his Manual of Anthropology says: 



All this shows that a more considerable growth of the frontal cerebrum, 

 as occurring in some brachy cephalic groups, is to be considered the cause 

 of metopism. By the internal pressure the normal concrescence of the 

 frontal bones is prevented, likewise in hydrocephalic skulls, in which 

 regularly the metopical suture persists. 



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