THE ARTERIAL BLOOD-PRESSURE IN A MAMMAL 269 



a. Bare the left arm, and wrap the rubber sleeve band snugly just 

 above the elbow and turn the free end under at the top. Connect the 

 Tyco or Faught manometer with one entrance tube and the bulb pump 

 with the other. 



Lightly bind the bell of a stethoscope over the brachial artery on the 

 inner surface of the forearm just under the border of the arm band. 



b. Quickly fill the band to a pressure of 150 mm., i.e., completely com- 

 press the brachial artery. Slowly allow the air to escape, listening care- 

 fully with the stethoscope for the first appearance of a pulse murmur in 

 the artery. At the same time watch for the appearance of oscillations 

 in the dial of the manometer. At a certain pressure the hand of the dial 

 will suddenly begin to oscillate and a distinct intermittent sound clear 

 and sharp in tone will be heard. This is the moment when the first escape 

 of blood through the compressed artery takes place. It measures the 

 systolic pressure, c. Continue to reduce the pressure. The oscillations 

 of the dial will increase up to a certain point. An intermittent pulse will 

 be heard passing into a loud and sharp snappy sound. At a certain 

 point the sound suddenly becomes dull and low and disappears. The 

 point of maximum oscillation and of disappearance of the intermittent 

 sound marks the diastolic pressure. 



Measure the pressures in the standing position, in sitting position, 

 and after a short run. Tabulate the results and draw averages. Repeat 

 the measurements on children and elderly people, using care not to pro- 

 long the total compression of the artery. 



14. The Arterial Blood-Pressure in a Mammal. The arterial blood- 

 pressure may be measured on the anesthetized cat, dog, or rabbit. Simple 

 blood-pressure was originally measured by Hale's method of connecting 

 the artery with a vertical tube and allowing the blood to flow freely into 

 the tube until a column was raised to the height which balanced the pres- 

 sure in the vessel. This simple method is decidedly the best for the 

 beginner, since it does not necessitate the use of very complicated appara- 

 tus. At the same time it gives practice in anesthesia and in operations 

 under anesthetics, and therefore serves as a good preparation for the more 

 complicated experiments which follow. 



The necessary apparatus should first be prepared as follows : A vertical 

 tube supported on a stand with a scale graduated in the metric system, 

 assorted cannulae of approximately the size of the carotid artery of the ani- 

 mal to be operated on, linen-thread ligatures, dissecting set in good condition, 

 an animal-holder with strings or straps firmly to fasten the anesthetized 

 animal, a chloroform-ether mixture for dogs (or other anesthetic according 

 to the animal to be used). Four men should be assigned to perform this 

 experiment. While two are chloretonizing, anesthetizing and preparing 

 the animal, two should arrange the apparatus as nearly ready for con- 



