36 L. BOLK 



of the first two individuals of the table, was unable to prevent 

 the coalescence of the two frontal bones, it is wholly unthink- 

 able that a somewhat increased development of the brain will 

 suffice to prevent these bones from uniting. 



One may advance still another more weighty question with 

 regard to the influence of the growing brain upon the skull. It 

 is assumed that the pressure exercised by the growing brain upon 

 the inner surface of the skull rises, when the brain is developing 

 in a greater degree. Is this assumption true? I do not be- 

 lieve it. It seems to me more probable that with regard to the 

 expansion due to their grow^th, the brain and the skull form one 

 entity, the same hereditary factors determining the growth in- 

 tensity of the brain as well as of the cranium. I do not believe 

 that the dilatation of the latter is a mere mechanical phenome- 

 non, depending on the pressure exercised by its contents. To 

 some degree this may be the case in pathological circumstances, 

 as in hydrocephaly or in premature closure of some suture or 

 other, but under normal circumstances, I believe the intra- 

 cranial pressure always to be the same, varying only between its 

 physiological limits. 



As a further argument in favor of the assumed influence of 

 the growing brain upon the expansion of the skull, the fact is 

 advanced that the forehead in metopical skulls is broader than 

 in those with normal closure of the frontal suture, this increase 

 of the transverse frontal measure being another result of the 

 more strongly developing frontal lobes of the brain. Without 

 doubt, the observation made f. i. by Welcker and Papillante is 

 right, and I am able to confirm the same, the metopical skulls 

 of my collection having an average breadth of the forehead of 

 99.7 mm. and the nonmetopical one of 96.5 mm. But I cannot 

 agree with the interpretation of the phenomenon given by the 

 above mentioned authors. I think in this matter they are con- 

 fusing cause and effect. The difference may be elucidated in 

 the following way. If the frontal suture does not disappear 

 during the second year, the apposition of bony tissue in it is con- 

 tinued during a longer space of time than in case of its disappear- 

 ance in the normal way, and therefore there is a very favorable 



