THE RESPIRATORY SYSTEM, INCLUDING THE LARYNX 273 



the surrounding tissue. In other words he claimed that the cartilago 

 lateralis had a dual origin. 



Gegenbaur's theory was very similar except that he thought that 

 the whole cart, lateralis was derived from the fifth branchial arch, and 

 that the M.. transversus ventralis was homologous with the constrictores 

 arcuum of that arch. Goppert ( 1 8 94) accepted Gegenbaur's theory and 

 said that the M. dilatator laryngis represented M. levator arcuum F, 

 and was therefore the homologue of the levatores of the branchial 

 arches. He opposed Wilder's theory as to the derivation of M. con- 

 strictor laryngis on the ground that it is a striped muscle, while the 

 circular muscle of the alimentary canal is of course composed of 

 smooth elements. 



In 1896 Wilder returned to the subject. He renounced his former 

 theories concerning the dual origin of the cart, lateralis and deriva- 

 tion of the ring of muscle round the larynx from the muscles of the gut, 

 and accepted the views of Gegenbaur and Goppert. Goppert (1898) 

 also abandoned his former theory that the M. laryngeus ventralis is 

 derived from the transverse muscle of the fourth branchial arch and 

 said that it was really a serial homologue of this and represented 

 the M. transversus ventralis V. 



In 1 90 1 Druner published his classic work on the visceral skeleton 

 and its muscles in Salamandra and Triton in both larval and adult 

 stages. He declared a general acceptance of the current theories but, 

 on the ground of innervation, suggested that the laryngeal skeleton 

 and its muscles were not derived from the fifth branchial segment but 

 from the sixth or some more posterior arch. 



Wiedersheim (1904) was the first to put forward the suggestion 

 that perhaps the cart, lateralis of Amphibia had no connexion with 

 the visceral arches after all, but was rather a supporting structure 

 produced independently in response to muscular pressure. This 

 suggestion was based on his study of the Ganoid and Dipnoan 

 fishes [Zool. Jahrb. Suppl. vii, pp. 1—66). 



Edgeworth (1920) turned Wiedersheim's suggestion into an 

 established fact. After giving an anatomical description of the de- 

 velopment of the laryngeal structures in various Amphibia, he 

 reviews the work of previous investigators and then summarizes 

 his own conclusions in the following words : 



'The arytenoid s. pars laryngea cartilaginis lateralis of Amphibia is developed 

 within the constrictor laryngis, or within this and the laryngei, and like them is 

 differentiated from cells from the splanchnic layer of the coelomic epithelium. 

 It does not therefore represent a fifth, or a more posterior branchial bar. Its 

 development is probably, as Wiedersheim suggested, dependent on muscular 

 4038 T 



