Fig. 249. Tracing showing the action of arecoline and of atropine on intrathoracic 

 pressure, bladder contractions and blood-pressure in a dog. Intrathoracic pressure was 

 recorded by means of a tambour with a moderate! v tightly stretched rubber membrane. 

 The tambour was connected with a glass tube which was passed into the chest cavity 

 (without letting air in:o the chest). Arecoline strongly contracts the bronchioles and 

 thus shrinks the volume of the lungs. This drew air out of the tambour into the chest 

 and caused the writing point to write at a lower level. The bladder and heart both show 

 a marked reaction to the drug. These effects are partially counteracted by the atropine. 



