160 



ON THE STRUCTURE OF THE SKULL. 



The axis of the second visceral arch becomes converted 

 above into the stapes, below into the styloid cartilage, the 

 stylohyoid ligament, and the lesser cornua of the hyoid bone, 

 the body and greater cornua of which are developed from 

 the third visceral arch. Between the styloid cartilage and 



Fig. 64. 



Fig. 64. — Part of the skull ot a human foetus at about the sixth month, dissected to show 

 the auditory ossicles and Meckel's cartilage, Mck. Gl, the glenoid cavity. The 

 margo tympanicus and adjacent parts of the squamosal are represented as if they were 

 transparent, in order to show the position of the malleus (m) and incus (ij. The 

 tympanic bone (Tty) is merely indicated. Co., the cochlea. 



the stapes it is modified so as to form the stapedius muscle. 

 A centre of ossification appears in the styloid cartilage, and, 

 extending upwards and downwards, gives rise to the pyramid 

 and the styloid process. 



Some authors, however, give a somewhat different account 

 of the metamorphoses of the cartilaginous axes of the first and 

 second visceral arches to that which I have detailed, and which 

 is based chiefly upon the researches of Meckel, Rathke, and 

 Eeichert. Thus Gunther,* while he agrees with Reichert 

 that the cartilaginous axis of the first visceral arch divides 

 into three portions, the uppermost of which (that which is 

 primitively connected with the skull) early disappears, while 

 the middle and lower become converted respectively into the 

 incus and the malleus with Meckel's cartilage, differs from 



* Beobachtungen iiber die Entwickelung de.s Ochororgans bei Menschen unci 

 hoheren Saugetliu ion. 1842. 



