REACTIONS OF A. TIGRINUM 261 



passing through the respiratory mechanism and their direction 

 and disposal. 



BUnded adult Amblystoma were used on account of the ease 

 with which they can be handled as well as the fact that they show 

 less reaction to the light stimulus occurring under the conditions 

 necessary for observation. 



The animals were placed in a flat glass dish under the binocular 

 microscope and the water currents observed by means of a car- 

 mine suspension. Three different courses of these currents have 

 been observed. 1) A current taken in through the nasal open- 

 ings and expelled through the mouth. This condition is the 

 customary one persisting during the state of rest of the animal. 

 2) A current entering through the nasal passage and the mouth 

 and expelled through the same channels. This is the condition 

 occurring under stimulation, both the incurrent and the excurrent 

 phases taking place with a quick spurt. 3) A current of water 

 expelled through the nasal passages (this being the discharge 

 of the content of the buccal cavity), a special case occurring 

 only when the animals comes to the surface to obtain 'gulps' 

 of air. Air is taken in either through the nose or the mouth. 

 The latter is used for the quick 'gulps' of air which the animal 

 secures as it appears momentarily upon the surface, while the 

 nasal apertures are used when the animal is in a state of rest, 

 lying in the water with the snout protruded above the surface. 

 The current designated above as 3 occurs infrequently as the 

 aftermath of the second method. As a stimulus becomes at- 

 tenuated by diffusion, the animal seems to take in water more 

 quickly through the mouth that it can be discharged. At such 

 a time the currents seem to be simultaneously going into the 

 mouth and out through the nasal passages.^ 



2 Vincent and Cameron find that respiratory movements cease in the frog as 

 soon as the nares of the animal are under water. This condition has been 

 observed by them over several weeks. A preliminary set of experiments, in 

 which normal, anaesthetized and decerebrate frogs were used, shows that the inhi- 

 bition of the respiratory movements is temporary and that water currents can be 

 detected by means of the method given above. The efficiency of the valves 

 covering the nares decreases with the time of immersion. None of the animals 

 used in this work survived twenty-four hours of immersion. 



