OBLITERATION OF SUTURES IN SKULL 507 



frequency of the obliteration in general. For by the irivestigra- 

 tion of Fredericg and Ribbe it is made clear that total oblitera- 

 tion of the sagittal suture in the adult required a fairly long 

 period. Taking this fact into consideration the large number of 

 entirely closed sutures in infantile skulls awakes a strong sus- 

 picion that the obliteration, beginning in an early period of 

 life, proceeds more quickly than those taking place in the more 

 advanced phase of life. The increased intensity of all physio^ 

 logical and histological processes natural to youth, evidently 

 influenced also the process of premature obliteration. 



Now we will enter into the problem whether the obliteration 

 of the infantile skull is pathological or not. It is clear that 

 this problem is not solved by observing that the union of the 

 two parietal bones, when occurring at an early date in life, causes 

 deformity of the skull to a certain extent, for the effect of an 

 intrinsically normal process may become under circumstances an 

 abnormal one, while the proper nature of the process is not al- 

 tered by it. One must distinguish formal and causal genesis. 



Moreover one may not conclude that the closure must be of 

 a pathological nature only because it occurs before the full 

 development of the body is reached. For (1) many sutures 

 in the skull disappear during this stage of life and, (2) I call 

 attention to the result of my investigation in which I showed, 

 after examination of about 800 skulls of apes and monkeys,^ 

 that in a large number of genera of primates, and especially 

 in anthropoids, synostosis of the sagittal suture happens before 

 the individual is full-grown. Thus, in forms with which the 

 human being stands in close phylogenetical connection, the 

 premature synostosis of the two parietal bones appears to be 

 normal. Here the process bears a purely physiological character. 

 Why should we refuse then to consider it also physiological in 

 man? These arguments however are purely theoretical and 

 through them a decisive answer to the question proposed is 

 not possible. Let us try to find it, by examining more closely 

 the contents of table 3. It showed us that in infantile skulls 



2 Zeitschrift fur Morphologie und Anthropologie, B. 15, 1912. 



