288 SWALE VINCENT AND A. T. CAMERON 



enced through the muscular sense of the throat muscles acts as 

 the afferent stimulus for the reflex. 



B. BIRDS 



The respiratory reflexes in the duck have been dealt with in a 

 series of papers by Frances M. Huxley. 10 ' 11,12 This observer, 

 who makes no reference to the work of Fredericq, noted that 

 respiration in the duck always ceased when the head and neck 

 were immersed in water. In her conclusions she says ( 10 , p. 152) : 



Thus submersion of a duck's head gives rise to complete apnoea 

 followed by a compensatory hyperpnoea. Submersion of the end of 

 the bill does not produce this ; submersion of the external nares does so 

 only to a certain degree. For its complete production entire immersion 

 of the glottis, the anterior portion of which lies 2.5 cm. behind the 

 posterior border of the external nares, is required. 



In her second paper published on the same date she seems to 

 have somewhat altered her opinion. Here she states: "As soon 

 as the mucous membrane of the nostrils, etc., comes in contact 

 with the water, a reflex apnoea is produced" ( u , p. 174). 



Her detailed description of experiments points to the latter 

 view as being the more correct. Both with immersion of nostrils 

 and immersion of the whole head there was a comparable per- 

 centage of cases where one or two respiratory movements were 

 made after immersion. 



We have made several immersion experiments with the duck, 

 and we believe complete immersion of the nostrils (and not 

 necessarily of the whole head) is sufficient to induce apnoea. 



Doctor Huxley appears to assume that the mechanism is a 

 reflex from the mucous membrane of the nostril, as Axenfeld 

 assumed in the case of the frog, but her experiments did not 

 eliminate the possibility of a mechanical factor, such as we have 

 stated to be efficient in the latter animal. Such a mechanical 

 factor, however, does not appear to be in operation in the case 

 of the duck. 



Plugging the nostrils does not interfere with the normal 

 breathing in the duck, but this is partly due to the fact that the 



