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Scientific Proceedings (129) 



(6). Above the cup a lens (7) is placed for the purpose of 

 magnifying the stage. 



In use, pressure is made within the cup by means of the 

 rubber bulb. The membrane presses against the ear vessel and 

 the pulsations are observed by means of the light transmitted 

 from within the stage. When pulsations cease, the pressure is 

 read in millimeters of mercury on the "U" tube. 



Factors Which Vary the Pressure 



Age. It was found that age has a definite influence on the 

 pressure. Unless the rabbit is full-grown the pressure is in- 

 clined to be low. 



Excitation. Anything which excites the animal increases the 

 pressure. Six rabbits which were mildly excited by lifting them 

 from the table by the ears and gently rubbing the ribs showed 

 an average rise of 13.3 mm. 



Heat. Warming the ear by any means, or rubbing it with 

 the fingers, causes a definite rise which may be as great as 20 

 mm. This seems to be because of the vaso-dilation. 



Exercise. Almost any small amount of exercise raises the 

 pressure. The ten readings were taken in rapid succession. At 

 the third reading the animal stood up, stretched, and lay down 

 again. As a result the pressure promptly rose 10 mm., but im- 

 mediately returned to its former level. 



The pressure readings must always be made at the same point 

 in the vessel. The pressure decreases as the vessel becomes 

 smaller. 



Results obtained. The average systolic readings on various 

 individuals lie largely between 76 and 87 mm. Isolated read- 

 ings may run 90 or somewhat above and as low as 70. The 

 averages on nine rabbits, representing between 500 and 600 

 readings, are as follows : 



Rabbit 21 83 mm. Rabbit 25 78 mm. Rabbit 28 83 mm. 



Rabbit 23 85 mm. Rabbit 26 82 mm. Rabbit 29 79 mm. 



Rabbit 24 87 mm. Rabbit 27 82 mm. Rabbit 30 79 mm. 



Action of adrenalin. Subcutaneous injection of adrenalin re- 

 sults in a typical rise of pressure beginning from 10 to 20 minutes 

 after the injection. 



Sources of error. The greatest source of error seems to be 

 in the changes of vessel diameter due to vaso-motor stimula- 



