348 



F. H. EDGEWORTH 



backwards of the muscle, i.e. the posterior extension takes 

 place as fast laterally as in the mid-line. 



The posterior part of the Transversus ventralis v. forms the 

 ventral constituent of the Sphincter oesophagi et laryngis, but 



N.ordestj^ 



Const. oisoplx.. 

 Coivit. icuyrt^. 



Larynx 



Text-fio. 24. 



Const. Larvrtgr/^^ 



Con^t ce^oph 



trachea 



no distinction can be made between the muscles. They form 

 a continuous structure. The edges of the ventral constituent 

 slightly lap round the lateral edges of the oesophagus in a 16 mm. 

 embryo (Text-figs. 21, 22). 



In a 24 mm. embryo (Text-fig. 25) a downgrowth takes place 

 on each side from myotome x — downwards, backwards, and 

 inwards, towards the upper part of the oesophagus, a little in 



