THE DEVELOPMENT OF THE HUMAN SKULL. 151 



and mastoidea to their separate origins. This is tlie more re- 

 markable as, in his well-known paper on the "Ossification of the 

 Vertebral and Cranial Bones" (Meckel's " Archiv," 1 815), p. 636, 

 he states expressly that the mastoid process arises from a special 

 (••'litre. Possibly the omission arose from Meckel's supposing 

 that the exterior of the periotic mass is developed distinctly from 

 the proper bony labyrinth. 



Hallmann, in his well-known work, " Die Vergleichende 

 Osteologie des Schlafenbeins " (1837), does not cite the account 

 given by Meckel, and does not really improve upon the views of 

 Kerckringius. 



" In man, after, in the first place, the squamosal and then 

 the annulus tijmpanicus are formed, the os petrosum and mastoi- 

 ds um is still a common cartilage, which fills, externally, the gap 

 between the squamosal, the parietal, the supra-occipital and the 

 ex-occipital. When, in the fourth month, the cochlea and a 

 part of the semicircular canals, viz., the upper canal and the 

 anterior crus of the external canal, already consist of porous 

 bony substance, while the ossification of the posterior canal 

 (and probably of the posterior crus of the external canal) has 

 not proceeded so far ; the pars mastoidea appears as a single or 

 double nodule of the size of a millet-seed, which is deposited 

 upon the arch of the posterior canal, contributes to its ossifica- 

 tion, and now soon spreads over the whole cartilage, the four 

 neighbouring bones growing towards it. In Nos. 2543 and 9420 

 of the Berlin Museum, the insertion of this nodule upon the 

 petrous bone is quite distinct. This osseous centre appears in 

 the dry skeleton as an oval nodule, which I could easily scratch 

 off without injuring the canals, which proves that it arises as a 

 separate part." 



Lastly, Kolliker, in his recently published " Entwickelungs 

 Geschichte" (1861), sums up the present state of our know- 

 ledge respecting the ossification of the periotic cartilage as 

 follows (p. 320) :— 



"The ossification of the labyrinth does not appear to have 

 been investigated since the time of Cassebohm (' Tract, de Aure 

 Hum.,' Hal. et Magdeb., 1734 and 1735) and J. Fr. Meckel 

 ('Handb. d'Anat,' iv. p. 42, et seq.), which seems to be the 



