SOCIETY OP THE UNIVERSITY OF ABERDEEN. 



195 



It will be noticed that the increase in length of the occipital bone 

 in the skulls with a transverse occipital suture is 9 mm., or just under 

 one centimetre, but that the total length or arc from the Opisthion to 

 the nasion is increased by only 3'2 mm., showing that the increase in 

 length of the occipital bone has been chiefly at the expense of the 

 parietal and frontal bones. It will also be noticed that there is an 

 average increase of 37 cubic centimetres in the capacity of the skulls, 

 with an interparietal bone, as compared with that of normal skulls. 

 Now, if we pass to the third class of abnormality of the cranial sutures, 

 namely, sutures which occur in situations in which they are not 

 normally present at any period of life, we again find a confirmation of 

 the general law, that growth of the bones of the skull takes place at 

 right angles to the lines of the sutures. 



I have measurements of three cases in which the parietal bone 

 of one side is divided by a suture into an upper and a lower segment. 

 All of these cases show that there is increased growth in a direction 

 at right angles to the abnormal suture, and they also show that this 

 is, to a certain extent, although not entirely, compensated for by a 

 diminution in the bones of the opposite side. 



I shall allude first to two cases which were recorded by Gustav 

 Schwalbe. Both of these occurred in hydrocephalic children ; a fact 

 which appears to point to a causal connection between increased 

 intracranial pressure during the growing period, and the formation of 

 additional sutures, such as the intraparietal. 



The first case was a specimen of a full-time hydrocephalic foetus, 



