INHIBITORY RESPIRATORY REFLEX IN FROG 289 



animal breathes through the mouth. Surrounding the mouth 

 cavity with water and subsequently plugging the nostrils, does 

 not interfere with respiratory movements. Further, immersion 

 of the head in water while the nostrils are plugged with the 

 fingers has no effect, although on removing the fingers from the 

 nostrils while the head is still under water all respiratory move- 

 ments are immediately inhibited. This seems to us conclusive 

 evidence that in the duck a fluid contact with the mucous mem- 

 brane of the nostril is essential to the reflex. 



We can fully confirm Fredericq's observation that pouring 

 water over both the nostrils will bring about the apnoea, although 

 the mouth is freely exposed to air. Further, we find that a 

 stream of water directed through the nostrils produces the same 

 effect. Plugging one nostril with the finger and directing a 

 stream of air (under pressure) against the other induce the 

 reflex, but this may be due to distention of the air sacs, which 

 produces apnoea, according to Baer. 2 Stimulation by introduc- 

 ing a solid object into the nostril (such as wires, india-rubber 

 tubing, etc.) is not effective. 



It thus appears that the apnoeal reflex in the bird is of a 

 similar nature to the more important one in the frog. 



The postural reflex fully described by Huxley and by Paton 14 

 in the duck may be easily demonstrated, and we have no further 

 observation to offer upon this phenomenon. Whether there is 

 a similar reflex in the frog we cannot yet be sure. What we at 

 first thought to be a postural reflex in that animal seems con- 

 nected with closure of the nostrils, and is probably something 

 different. 



We have carried out a series of experiments upon the pigeon. 

 Immersion of the nostrils in water or direction of a stream of 

 water upon the nostrils immediately stops the respiratory move- 

 ments. A stream of air under pressure produces the same effect 

 as in the duck, but this may be due to distention of air sacs 

 (see above). On the other hand, plugging the mouth and nos- 

 trils and mechanical and electrical stimulation are not effective. 



