DEVELOPMENT OF THE HUMAN LARYNX 33 



do not unite. These may later bridge across to form the m, 

 interarytaenoideus, but of that point, I am by no means certain. 

 No trace was found of the m. aryepiglotticus or the m. thyreoepi- 

 glotticus. The m. cricothyroideus » is fairly well developed, 

 though not nearly so far advanced in form and size as the m. cri- 

 coary taenoideus posterior. It is the only one that shows any tend- 

 ency to relation with the pharyngeal musculature, and Frazaer 

 considers them to have the same origin. In general the muscula- 

 ture of the larynx is rather better defined than the cartilages at this 

 period. Strazza in 1888, completed the only really valuable work 

 done on the development of the human laryngeal musculature. 

 Nothing of importance has been added since his paper. He thinks 

 that the laryngeal, tongue and pharyngeal musculature develop 

 out of one and the same muscle mass, which in the early embryo 

 develops from an isolated 'muscle island,' which exists independ- 

 ently of the muscle plates. And that the premuscle tissue of the 

 tongue and larynx is a continuous one, the latter merely lying 

 inside the former. In the region of the epiglottis and larynx, 

 he thinks, is also contained the premuscles masses, though he 

 cannot differentiate them at all in his youngest embryo (12 to 13 

 mm.) . He associates the simultaneous development of the tongue 

 and larynx musculature from the same source, with the fact of the 

 union in speech between the muscles of the tongue and larynx. 

 This is an attractive theory, but my observations cannot substan- 

 tiate his statement. There is no indication that the larynx mus- 

 cles develop from the myotomes, on the contrary, they appar- 

 ently arise from the ventral visceral mesenchyme which continues 

 up into the floor of the mouth. Bvt in this 10.5 mm. embryo in 

 which even certain larynx muscles can he isolated, there is no asso- 

 ciation with the tongue musculature, and hut little with the phar- 

 yngeal set. In earlier stages the cells which are to form the 

 premuscle masses cannot be distinguished by our present methods 

 from other cells of the condensed mesenchyme of this region. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 12, NO. 1 



