Abstract
The carotid sinus is the seat of reflexes controlling heart rate, blood pressure and respiration. This fact was first demonstrated in acute experiments by H. E. Hering, 1 and has been amply verified by Heymans, 2 Danielopolu, 3 De Castro, 4 and by one of us (Cromer). The following work was undertaken to study the effects of exercise before and after denervating the carotid sinus to ascertain how vital is the rôle played by the carotid sinus mechanism.
Method. Dogs were trained so that heart rate, blood pressure and respiration rate could be determined under basal conditions. After 21/2 or three minutes of vigorous exercise, readings were again taken After a number of control observations had been made over a period of several weeks, the dogs were operated aseptically and the carotid sinus nerve, or Hering's nerve, and the carotid glomerulus and plexus were removed and the carotid sinus region was painted with phenol bilaterally.
Beginning on the day following the operation and thereafter for from 2 to 8 weeks, heart rate, blood pressure and respiration rate were followed before and after exercise.
The accompanying table gives the average results on 5 dogs. The results on the individual dogs compare closely with the results shown in the table.
The slight variation in the data obtained before and after denervation of sinuses indicates that the physiological role of the carotid sinus as a reflexogenic center for controlling blood pressure, heart rate and respiration is readily taken over by other mechanisms in the dogs.
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