72 THE LUNGS, BY FRANZ EILHARD SCHULZE. 



wall, are of small size, and run transversely round the ultimate 

 air passages, anastomosing frequently, and forming narrow lon- 

 gitudinally elongated meshes. I have not been able to demon- 

 strate the existence of an epithelium covering them, though 

 one is probably present. 



Between the pulmonary canals there is a clear fibrous inter- 

 stitial connective tissue, which in some birds, as the Goose and 

 Duck, is of moderate thickness ; whilst in others, as the Pigeon, 

 it is scarcely appreciable. 



The air-sacs of the Bird, which may be regarded as local 

 projections of the bronchial wall, consist of fibrous connective 

 tissue intermingled with delicate elastic fibres, and are traversed 

 by a wide-meshed capillary plexus ; on their inner surface they 

 possess a simple pavement epithelium, the cells of which bear 

 cilia only in the vicinity of the orifices. 



PRINCIPAL WORKS ON THE MINUTE ANATOMY OF THE 

 LUNG OF THE BIRD. 



FULD, De organis, quibus aves spiritum ducunt, 1816. 



RETZIUS, Froriep's Notizen, Bd. xxxv., p. 1, 1832. 



LEEEBOULLET, Anatomie comparee de 1'appareil respiratoire dans les 



animaux vertebres, 1838. 

 E. WEBEE, Ueber den Bau der Lungen bei den Yogeln, im Bericht 



iiber die 19. Versammlung deutscher Naturforscher und 



Aerzte in Braunschweig, 1842. 

 GUILLOT, Recherches sur 1'appareil respir. des Oiseaux. Annales des 



Sci. nat., 1846. 



SAPPEY, Recherches sur 1'appareil respir. des Oiseaux, 1847. 

 RAINEY, On the minute anatomy of the lung of the Bird, in Medico- 



Chirurgic. Transactions, Tom. xxxii., 1849. 

 EBEBTH, Ueber den feineren Bau der Lunge in the Zeitschrift fur 



wissensch. Zoologie von v. SIEBOLD und KOLLIKEE, 1863. 



III. STRUCTURE OF THE LUNG IN REPTILES AND AMPHIBIA. 



The lungs of Reptiles and Amphibia agree so closely in 

 their structural relations, that they may here be considered 

 together. 



In the continuous series of forms presented by these animals 

 in regard to the structure of their respiratory organs, the Tritons 



