VIII 



THE RESPIRATORY SYSTEM, INCLUDING 

 THE LARYNX 



THE RESPIRATORY SYSTEM (PI. XXIII, %. 77) 



Under this head it is proposed to consider those structures usually- 

 regarded as directly associated with the physiological process of 

 respiration, namely the glottis, the laryngo-tracheal chamber, the 

 bronchi and the lungs, and finally, to review the physiological aspect 

 and to discuss the probable means by which re-oxygenation of the 

 blood is brought about in the adult Salamander. 



As is well known, the Caducibranchiate Urodeles employ the 

 'buccal-force-pump' method of breathing similar to that of the 

 familiar Frog. This involves the presence of mechanisms for closing 

 the nares, and for raising and depressing the floor of the mouth, 

 but, as such structures are only secondarily subservient to respira- 

 tion, they are described elsewhere in their appropriate places (see 

 pp. S5 and 303). 



1. The Glottis. 



The glottis (gts.) is a small slit-like aperture lying longitudinally 

 on the floor of the pharynx. It is raised only very slightly above the 

 level of the surrounding tissues, and leads directly into the laryngo- 

 tracheal chamber. 



2. The Laryngo-tracheal chamber. 



The laryngo-tracheal chamber (tr.ch.) is a more or less triangular 

 cavity. The glottis opens into the apex, antero-dorsally, while the 

 posterior basal angles merge into the bronchi. The whole structure 

 lies immediately dorsal to the truncus arteriosus, which thus forms 

 a useful landmark for dissection purposes. The sides of the chamber 

 are supported by a series of semicircular cartilages, the whole series 

 forming the cartilage lateralis (Edgeworth),^ while the anterior pair 

 are distinguished as the pars laryngea s. arytenoid (Edgeworth), and 

 the remainder as the pars trachealis (Edgeworth). The arytenoid 

 cartilages (c.ary.) bound the sides of the glottis and are approximated 



' The synonyms of other authors are sufficiently obvious to render citation un- 

 necessary. 



