374 SPECIAL HISTOLOGY. 



cranium, for instance, as the primary ossific points first appear 

 in the situation of the tuberosities of the parietal and frontal 

 bones, the bones are at first placed widely asunder, and are 

 connected merely by a fibrous membrane, the continuation of 

 the periosteal lamella of each, and which is united on the 

 internal aspect with the remains of the membranous cranium 

 of the embryo, and with the dura mater. The bones then 

 continue to grow towards each other, and at last, constantly 

 advancing in the above-described continuation of the peri- 

 osteum, come very nearly into contact at the frontal and 

 sagittal sutures ; there remains, however, for a long time, one 

 large vacuity, in particular, between them, — the anterior fon- 

 tanelle, — but which closes in the second year after birth ; whilst 

 at the same time, the bones, which, up to this period, adjoined 

 each other with a straight line of juncture, send out inter- 

 digitating tooth-like processes, till ultimately, when their 

 blastema is wholly consumed, they continue united only by 

 the remains of the periosteum (the sutural cartilage, as it is 

 termed, or better, the sutural ligament), but which also is 

 capable of becoming ossified sooner or later, and, indeed, in- 

 variably first on the inner aspect of the suture, where the 

 tooth-like processes are very little developed. The changes of 

 form in the entire bones during their development are very 

 remarkable, and have hardly been attended to. If a parietal 

 bone, for instance, of a foetus or new-born child, be compared 

 with that of an adult, it will be found that the former is much 

 more curved, and in no way at all represents a piece cut out 

 of the middle of the latter. The adult parietal bone con- 

 sequently must have undergone a very important alteration in 

 the curvature of its surfaces, and this, as mechanical conditions 

 are out of the question, can only have been effected by an 

 unequal deposition of bone internally and externally, in the 

 middle and at the borders ; or by deposition on the one side 

 and absorption on the other. That unequal deposition does 

 actually occur, is seen, for example, in the juga cerebralia and 

 impressiones digitatce, the sulci meningei, &c; but it appears to 

 me, that the whole matter cannot be understood, unless we 

 assume that local absorptions also take place in certain situa- 

 tions. How otherwise can be explained the increase in breadth 

 of the superior orbital ridge, the increase of distance between 



