414 SURGEON J. 0. THOMPSON ON THE 



32. Contributions to the Anatomy o£ the Ophidia. 

 By Joseph C. Thompson, Surgeon, United States Navy *. 



[Received April 25, 1913 : Read June 3, 1913.] 

 (Text-figures 77 & 78.) 



Index. 



Page 



Sugeestiou as to the Possible Origin of the so-called Tracheal 



"Lung 414 



Notes upon the Anatomy of : — ■ 



JCenopeltis tmicolor 415 



Cyclocorus lineatus 419 



Chrysopelea ornata 420 



Crotalus confluentus 422 



The Intromittent Organ in : — 



Folyodontophis bivittatus 423 



Tropidonotus vihakari 423 



Selicops angulatus 424 



Cyclocorus lineatus 425 



Spilotes pullatus 425 



S3' stein atic : 



Sebius, gen. nov 424 



/Stcggestion as to the Possible Origin of the so-called 

 Tracheal Lung. 



It is suggested that the tracheal membrane has been developed 

 as a device originally contributing to the required flexibility 

 of the tube. The cartilaginovis rings being interrupted behind, 

 or on one side, permit that the structure be subject to a much 

 greater pressure, especially when bulky morsels are being 

 swallowed, than would be the case were the rings complete. 

 The tracheal membrane, being continuous with the lung, appears 

 to have afforded a convenient foundation for the extension of 

 pulmonary tissue when the need for an increased breathing 

 surface has arisen, or when the lung has been encroached upon 

 by other organs. 



In the Hydrophidse an increased pulmonary area is required 

 both to give buoyancy and to enable the sea-snakes to remain 

 some time beneath the surface. The most specialized species in 

 the genus Hydrophis Daudin, those in \\\q fasciatus group, possess 

 a lung that extends nearly to the vent, and a tracheal lung of 

 due proportion. 



In the Acrochordinfe, the members of which are of aquatic 

 habits, there is also a highly developed tracheal lung. Owing to 

 the abnormal size of the heart the respiratory tissue on the 

 trachea is widely separated from the lung itself. 



In the Viperidse the elaboration of venom requires a large 

 liver. These serpents as a rule have short and thick bodies, and 

 the liver invades the region just caudad of the heart. As a 



* Communicated by Dr. F. E. Beddaed, M.A., F.R.S., F.Z.S. 



