500 



L. BOLK 



TABLE 2 



on both sides the suture was partially or entirely closed are men- 

 tioned once, and also those in which the suture on one side only 

 was partially obliterated. Moreover an uncertain number re- 

 mains in which the suture is totally closed on one side. Tak- 

 ing this into consideration, I found amongst about 1820 skulls 

 of non-adults at least the number of 63 + 25 + 44 + 40 = 172 

 with closure of the masto-occipital suture either on both sides 

 or on one side only. Reckoning the number of skulls with a 

 total closure on one side to be 10, we can conclude that in 10 

 per cent of our non-adults the said suture shows more or less 

 signs of obliteration. Therefore Fredericg's conclusion is not 

 right, when he writes that the coalescence of the petrosal and 

 occipital bone in the third decennium of life rarely occurs. Even 

 before the twentieth year the coalescence is not exceptional. 

 The preceding table shows yet another phenomenon of no less 

 importance. At what age does this obliteration take place? 

 Our table includes skulls from about three years up to the adult 

 state. Now two possibilities must be considered. Either the 

 coalescence may begin at each date of this period, or the com- 

 mencement of the process is limited to a shorter or longer phase 

 of it. In the first case the number of synostotic skulls increases 

 while the age advances; in the second case such a correlation is 

 wanting. Now for the solution of this problem it is a happy 

 coincidence that the number of skulls in Group I is considerable. 



