Role of naso‐buccal passages in thermoregulation in sheep

Abstract

1. Experiments with a face‐mask in which the temperature of the air in the face‐mask was raised to 40° C while the ambient temperature in the chamber was maintained at 20° C, resulted in a marked increase in respiratory frequency and a slight decline in carotid blood temperature of unshorn sheep. Partially shorn sheep showed only small respiratory responses. 2. Localized infra‐red irradiation of the naso‐buccal area of unshorn sheep also resulted in an increased respiratory rate. 3. It is suggested that the initiation of polypnoea during infra‐red irradiation of the naso‐buccal region and following rise in the temperature of the air in the face‐mask is due to stimulation of warm receptors in the upper respiratory tract. 4. Cooling the naso‐buccal air in the face‐mask to 10° C after thermal polypnoea had been established at an ambient temperature of 40° C resulted in a moderate decline of 30–40 respirations/min. This decline was attributed to the stimulation of cold receptors located in the upper respiratory tract. © 1970 The Physiological Society