ON THE REFLEX NATURE OF APNŒA IN THE DUCK IN DIVING. II. REFLEX POSTURAL APNŒA

Abstract

There is still a considerable amount of work to be done on the variations in posture which affect—and as to what degree they affect—the respiratory centre of the duck, and on the nature of the receptive elements which bring about these changes. The results so far determined are as follows:— 1. A well‐marked reflex postural apnœa can be produced under the conditions brought about by extension or dorsi‐flexion of a duck's head and neck, when the animal lies upon its back. 2. Its value to the duck appears to be as a mechanism to aid it in resisting the inspiration of water when in the diving position. Apnœa, as well as other reflex phenomena associated with diving, can be readily produced by placing the duck in the diving position, quite apart from the presence of water. The appearance of the apnœa is not, however, as constant in this position as in 1. 3. The evidence also shows that the fact of extension or dorsi‐flexion of the neck plays a part in producing apnœa. 4. Breathing continues when the vertex of the duck's head faces upwards, and it stops when the vertex faces downwards. 5. Experiments made after having broken up the labyrinths indicate that their function upon respiration is twofold, causing it to continue in certain positions, e.g. vertex up, and stopping it in others, e.g. vertex down, and that after its destruction extension in all positions is generally capable of bringing about a pause in breathing.