THE CONNECTIVE TISSUES AND THE SKELETAL SYSTEM. 201 



proximal end of this rod is then replaced by bone which fuses with the temporal 

 bone and forms the styloid process. The distal (ventral) end is replaced by 

 bone which forms the lesser horn of the hyoid bone. Between the styloid proc- 

 ess and the lesser horn, the cartilage is transformed into the stylohyoid liga- 

 ment (see Figs. 177 and 180). 



In each half of the third branchial arch a piece of cartilage develops and 

 subsequently is replaced by bone to form the greater horn of the hyoid bone. 

 The two horns become connected at their ventral ends by the body of the hyoid 

 bone which is also a derivative of the third arch. Later the lesser horn fuses 

 with the greater horn to bring about the adult condition (Fig. 180). 



In the ventral parts of the fourth and fifth arches pieces of cartilage develop 



Incus Malleus 



Mandible 



I Ulil Hi III! "II 1111 li Illll II I 



Tympanic ring 



Stylohyoid lig. 

 Cricoid cartilage 



Thyreoid cartilage | Meckel's cartilage 



Hyoid cartilage (greater horn) 



FIG. 180. Lateral dissection of head of human foetus, showing derivatives of branchial 

 arches in natural position. Kollmann's Atlas. 



and form the skeletal elements of the larynx. A more detailed account of these 

 will be found under the head of the larynx (Chap. XIII). 



The auditory ossicles are also derived largely from the branchial arches, the 

 incus and malleus being derived from the proximal end of Meckel's cartilage (first 

 arch), the stapes having a double origin from the second arch and the embryonic 

 connective tissue surrounding the periotic capsule. But since they form inte- 

 gral parts of the organ of hearing, a discussion of their formation is best in- 

 cluded in the development of the ear (Chap. XVIII). 



The accompanying table indicates the types of development in the different 

 bones of the head skeleton. 



