522 L. BOLK 



TABLE 7 



Absolute frequency of premature obliteration 

 in 1820 skulls 



Sut. masto-occipitalis. . . . 



Sut. sagittalis 



Sut. squamosa 



Sut. parieto-mastoidea. . . 



Sut. coronalis 



Sut. parieto-sphenoidalis. 

 Sut. fronto-sphenoidalis. . 

 Sut. lambdoidea 



times 



272 



71 



17 



16 



12 



5 



5 



5 



occipitalis with 272 cases or 15 per cent and the sutura squamosa 

 with 17 cases, or 1 per cent is no less surprising than that of the 

 sutura sagittalis with 71 cases or 4 per cent and of the coronal 

 suture with 12 cases or 0.6 per cent. Once more it is demon- 

 strated by these relations that a premature obliteration of 

 the sagittal suture occurs more often than was formerly be- 

 lieved, while that of the masto-occipital suture occurs so often 

 that it can scarcely be considered an anomaly. 



From the annotations, collected during my investigation, I 

 finally will communicate a very interesting observation. As 

 generally known it may happen in the skull of man that the 

 sutura frontalis persists. According to the communications of 

 the authors, this should be the case in about 6 per cent. In 

 Dutch skulls the persistence of this suture is found in not quite 

 9 per cent. It has struck me, however, that I did not find 

 in my collection of non-adult skulls the coincidence of a per- 

 sisting sutura frontalis and premature obliteration in one of the 

 other sutures. This seems not inconceivable in case of the 

 sagittal suture, for this suture and the frontal can be con- 

 sidered as two parts of one, extending from the nasion to the 

 lambda. But also nearly the same was stated as to the masto- 

 occipital suture. There were, as mentioned, 272 skulls with 

 premature obliteration of this suture, but according to the 

 general relation, one should expect to find amongst these skulls, 

 9 per cent or 24 with a persisting metopical suture. In reality 

 I only found two cases. 



