290 SWALE VINCENT AND A. T. CAMERON 



C. MAMMALS 



According to Huxley, Beau 4 in 1860 observed that when a 

 dog is immersed in water it immediately ceases breathing, and 

 this was confirmed by Paul Bert 5 in 1870. Beau attributed the 

 cessation to reflex action from contact of water with the respi- 

 ratory orifices, while Bert considered it due to voluntary move- 

 ment. 



We have found that the reflex can be readily demonstrated 

 in the white rat. 



We have shown that if the snout of the non-anaesthetized 

 animal be immersed in water at body temperature (to avoid 

 effect of cold), even if part of the mouth remains in contact with 

 air, immediately the nostrils are immersed they are closed and 

 respiration ceases. 



Precisely the same occurs with the anaesthetized animal, and 

 the result can easily be recorded by the graphic method. The 

 reflex is very definite, and — with a short immersion lasting a few 

 seconds only — appears to persist for some seconds after removal 

 of the snout from water. 



The observation upon the anaesthetized animal is sufficient 

 to negative any suggestion of voluntary action. 



Further observations showed that a stream of air under slight 

 pressure stops the respiration, while plugging the nostrils and 

 mouth and mechanical and electrical stimulation do not do so. 



The same results are obtained with the anaesthetized rabbit. 



Although we are not yet prepared to discuss fully the nature 

 of the reflex in mammals, we think that it is probably of the 

 same nature as that in the duck. 



GENERAL SUMMARY 



In all vertebrates there appear to be reflex mechanisms which 

 inhibit the respiratory movements when the animal's head is 

 submerged beneath the surface of water. The receptors for 

 these reflexes are probably situated in the epithelium of the 

 nasal mucous membrane. In addition we have adduced some 

 evidence that in the frog there is an accessory reflex mechanism 



