66 H. L. Bruner 



observed by Gaupp (1896, p. 242) in the frog and by myself (Bruner 

 1896, p. 400) in the higher urodeles: 



1) Aspiration. The jaws are quickly thrust into the air and 

 the mouth is widely opened. At the same time the constrictors of 

 the gill arches probably increase their tonus. 2) Expiration. The 

 escape of air is indicated by the contraction of the abdominal walls 

 This stage is very brief and is usually complete while the mouth 

 is still open. 3) Inspiration. The entrance of air into the lungs is 

 marked by a wave which runs along the side of the abdomen from 

 its anterior to its posterior end. No air escapes from the nasal 

 cavity, which remains filled with water during the entire pulmonary 

 process. The muscles of the gill arches also prevent the loss of air 

 through the gill clefts. After Inspiration the glottis closes in order 

 to retain the air in the lungs. As the animal sinks to the bottom 

 a certain amount of air, probably a surplus remaining in the mouth 

 after inspiration, is forced out either between the lips or through 

 the gill clefts which are opened for the purpose. The removal of 

 this air is evidently a preparation for acquatic respiration, which 

 would be more or less hindered by the presence of air in the mouth 

 and pharynx. 



The intervals between respirations in Necturus vary according 

 to the temperature, freshness of the water, etc. In running tap water 

 at 56 ° F. six specimens showed no respirations during ninety minutes. 

 In a sinall quantity of water which had stood over night at a tempe- 

 rature of about 69° F. the average rate per specimen was nine 

 respirations per hour. In freshly changed water at the same tempera- 

 ture the rate feil to 5.7 respirations per hour. 



Siren. Pulmonary respiration in Siren is very similar to that 

 of Necturus. In the specimens studied, which were about twelve 

 inches long, the air was taken quickly, the animal exposing itself 

 as little as possible above the surface. Under normal conditions no 

 air escapes from the nostrils or gill clefts during inspiration and the 

 nasal cavity is probably filled with water during the entire pulmonary 

 process. The emission of surplus air is not so regulär as in Necturus, 

 but one or more bubbles may usually be secu, sometimes after a 

 considerable interval. 



Amphiuma. The respiratory movements of Amphiuma are slow 

 and the various stages of the process are easily distinguished. If 

 the animal is in water the floor of the mouth is strongly elevated 

 as the rostrum rises above the surface and by this means water is 



