518 



L. BOLK 



TABLE 6 



Obliteration of the masto-occipital suture in skulls in which also the sagittal suture 

 is totally or partially closed 



in which this combination coincides. It can be proved in the 

 following simple way. The frequency of the premature ob- 

 literation exclusively in the masto-occipital suture is 10 per 

 cent, that of the sagittal suture 3 per cent. Therefore, when 

 both phenomena were totally independent of each other a 

 combination of both should then according to the rules of proba- 

 bility never come to 1 per cent, as we have been able to de- 

 termine. Thus this very frequent coincidence can only be 

 explained on the assumption that the cause of the premature 

 obliteration in one of the two sutures at the same time increases 

 the predisposition to a simultaneous obliteration in the other 

 suture. In one of the preceding paragraphs I have developed 

 my view as to the cause of the obHteration. This too is sufficient 

 to explain the relative large frequency of the simultaneous 

 obliteration in the sagittal and masto-occipital sutures. 



The other cases in which together with the masto-occipital 

 suture yet another was obliterated were the following. In 

 three cases the masto-parietal and in one case the coronal suture 

 was obliterated simultaneously with the masto-occipital suture. 

 Finally I found a case in which the posterior half of the squamosal 

 suture and the whole masto-parietal suture were obliterated. 



On the whole there were found in my collection 24 infantile 

 skulls in which two sutures were coalesced. 



Finally there were amongst my material a small number of 

 skulls in which the premature obliteration had assumed a more 



