272 THE SALAMANDER 



by the M. constrictor laryngis and pulled apart by the M. dilatator 



laryngis. These muscles are described on p. 64. 



3. The Bronchi. 



The bronchi are short, wide tubes leading directly from the pos- 

 terior angles of the laryngo-tracheal chamber to the lungs. Their 

 epithelium is ciliated (Suchard). 



4. The Lungs. 



A very good account of the lungs has been given by Suchard ( 1 903), 

 who deals with their minute, as well as their gross structure. They 

 consist of a pair of small, heavily pigmented, conical sacs, pointed 

 posteriorly, and presenting a sacculated appearance externally. Their 

 cavities are not simple but are interrupted by trabeculae. According 

 to Suchard, two main longitudinal compartments may be recognized, 

 containing respectively the artery and the vein, together with sub- 

 sidiary longitudinal compartments formed around the arterioles and 

 venules, while the transverse septa are merely folds in the pulmonary 

 membrane. The same author states that smooth muscle elements 

 are present, but apart from these the lungs would be satisfactorily 

 compressed by the muscles of the abdomen. The lungs are not sus- 

 pended freely in the pleuro-peritoneal cavity as are those of the Frog, 

 but are firmly anchored dorsally to the body-wall by the pleural 

 mesenteries, and ventrally to the liver by the lig. hepato-cavo-pul- 

 monale (see also p. 269). 



Homologies of the Urodele Larynx. 



A great deal of work has been published on this question and 

 various authors have advanced different theories in an attempt to 

 demonstrate that the arytenoid cartilages and the laryngeal muscles 

 represent the remains of a transformed visceral arch. 



The discussion began in 1892, when Wilder and Gegenbaur 

 independently advanced similar theories. Wilder suggested that the 

 ■pars laryngea cartilaginis lateralis really represented the cartilage 

 of the fifth branchial arch of Selachians, and that the M. dilatator 

 laryngis was homologous with the dorsal segment of the muscles of 

 that arch. He also thought that the ring of muscle surrounding the 

 larynx — M. constrictor laryngis — was a continuation of the circular 

 muscle of the alimentary canal, and that X^sx&'pars trachealis cartilaginis 

 lateralis arose later than, and independently of, the arytenoids from 



