284 HISTORY OF THE HUMAN BODY 



In mammals the hyo-branchial support of the tongue is 

 reduced to a complex composed of a basi-hyal (body) and two 

 pairs of cornua, of which the anterior are typically the longer 

 and are formed by a chain of four skeletal pieces, cerato-, epi-, 

 stylo- .and tympano-hyal, the latter attached to the tympanic 

 region of the skull. The posterior cornua consist each of a 

 single piece, thyreo-hyal, connecting the body with the thyre- 

 oid cartilage of the larynx. In man the anterior cornua show 

 an unusual modification, the tympano- and stylo-hyals are 

 fused with the otic region of the skull, forming the styloid 

 process, the hypo-hyal is reduced to a rudiment which con- 

 nects with the styloid process by a ligament in which no trace 

 of the cerato-hyal is seen. Thus the anterior cornua, though 

 typically longer and more complex than the others, are spoken 

 of in man as the " lesser," an inheritance from the earlier 

 anatomical science in which comparison with other mammals 

 played no part. 



Inserted upon this skeletal complex as a basis there is de- 

 veloped in mammals a fleshy tongue composed of interlaced 

 muscular fibers, a part of which are intrinsic and belong to 

 the tongue itself, while others are extrinsic and consist of the 

 terminal fibers of other muscles. This organ is thus a struc- 

 ture totally unlike the tongue of most other vertebrates, in 

 which the skeletal support reaches through the organ and in 

 which motion is confined to a simple protrusion and retraction, 

 and resembles rather the fleshy lobe which appears in a few 

 cases appended to the other structure, as in the frog. More- 

 over, in some mammals, notably marsupials and lemurs, there 

 exists, beneath the fleshy organ, an accessory tongue-like struc- 

 ture, the sub-lingua, which possesses many attributes of the 

 tongue of the Sauropsida and like it is supported by a car- 

 tilaginous piece which may represent the os entoglossum. In 

 man the sub-lingua is reduced to a transverse fold, the plica 

 timbriata. readily seen if the mouth be opened and the tongue 

 elevated. If this organ be taken as the homologue of the 

 sauropsidan tongue, as its structure and position seem to indi- 

 cate, the fleshy tongue of mammals is a new structure, de- 



