The Mechanisni of Pulmonary Respiration in Amphibians with Gill Clefts. 65 



gill clefts. Water may, however, also be discharged through the 

 nasal cavity. 



In the frog larva water is taken, under moderate teinperatures, 

 both by the open mouth and through the nasal cavity. Under lower 

 temperatures the mouth is closed and water enters only through the 

 nostrils. It is expelled through the gill clefts, not through the nasal 

 cavity. 



Pulmonary Respiration. 



L. Vaillant (1863, p. 340) noticed the bubbles of air which 

 escape from the gill clefts of Siren after air is taken and concluded 

 that the gills are supplied with atmospheric oxygen in this manner. 

 Sometimes the supply of air, which is taken by the open mouth, 

 may be used only for this purpose, at other times it may be sent 

 directly to the lungs, or a part may be sent to the gills and the 

 remainder to the lungs. In Cryptobranchus japonicus B. G. Wilder 

 (1882) observed that the respiratory air is taken through the nostrils, 

 after which bubbles of air escape from the nostrils as the animal 

 sinks in the water. Smith (1907 gives the following details in regard 

 to the breathing habits of Cryptobranchus allegheniensis : »The air 

 taken in through the nares the instant the snout reaches the surface 

 is probably immediately afterwards mixed with respired air expelled 

 from the lungs; then the greater part of the mixed air is forced 

 back into the lungs by a swallowing movement. The surplus air 

 escapes through the mouth or gill slits as the animal sinks to the 

 bottom.« In A??iphiuma, according to Mrs. Wilder (1909), air fre- 

 quently escapes from the gill clefts during the act of inspiration, 

 while in Necturus it is often lost through both gill clefts and external 

 nares. 



In the following studies I have made use of Necturus maeulosus, 

 Siren lacertina, Amphiuma tridactylum, Cryptobranchus allegheniensis 

 and larvae of higher amphibians. The respiratory movements of 

 these forms will now be described and a basis will thus be laid for 

 the study of the respiratory mechanism itself. 



Necturus. When Necturus is immersed in water [the regulär 

 bucco-pharyngeal movements are interrupted at intervals by pulmonary 

 respiration. As a preparation for this process the floor of the bucco- 

 pharyngeal cavity is strongly elevated in order to remove as much 

 as possible of the respiratory water. This act is followed by the 

 succesive stages of pulmonary respiration, corresponding to those 



Morpholog. Jahrbuch. 48. 5 



