Syrinx uj Foai. 303 



Summary. 



In contlusion, the following points may be given as distinctive 

 features of the svrinx of the common fowl :— 



1. The formation of a syringeal chamber or " tympanum," with 

 exttjnsive membraneous Avails. 



2. The presence of membraneous internal bronchial walls, with 

 the connectinjr bronchidesmus. 



3. The presence of the bolt-like pessulus, with its ventral and 

 dorsal triangular plates. 



4. The very vestigial condition of the last five tracheal rings, 

 the greater development of the first two bronchial semi-rings, and 

 tlie close relationship of all these elements with the ventral and 

 dorsal plates. 



5. The very noticeable absence of nmscles in direct or intimate 

 association Avith the syringeal membranes. 



6. The complex and intimate relationsliip of respiratory air 

 sacs to the syrinx as a whole. 



Literature. 



Brunelli, G. — Riduz d. laringe sup e. svil d. siringe, etc. Gior- 

 nale ornitol. Ital. Siena, 1904. (Not available to me for con- 

 sultation.) 



Garrod, A. 0. H. — " On the conformation of the thoracic ex- 

 tremity of the trachea in the class Aves.'' Pt. I., Gallinae, P.Z.S., 

 1879, pp. 354-380. 



Hacker, V. — Ueber den unteren Kehlkopf der Singvogel. Anat. 

 Anz., 189S. pp., 521-532. Gesang d. Viigel, Jena, 1900. 



Juillet, A. — Recherches Anatomiques, Embryologiques. Histolo- 

 giques. et Comparatives sur le Poumon des Oiseaux. Proceedings of 

 Experimental and General Zoology, Vol. 49, Xo. 3, Chap. IV., Jan., 

 1912. 



Wunderlich. L. — Beitrage zur vergleichenden Anatomic und 

 Entwickelungsgeschichte des unteren Kehlkopfes der Vogel. 



Nova Acta Acad. Caes. Leop. Carol. CtMinanicae, Bd. XLVIll.. 

 1884. 



DESCRIPTION OF PLATES XVIII-XXIV. 



Figs. 1-3. — Median frontal or longitudinal horizontal sections 

 through the tracheo-broncliial junction of the chick embryo 

 at three stages, showing cliiefly the elements of the cartil- 

 aginous framework, the develupinir membranes and the air 

 sacs in relation to the syrinx. 



