12 



GENERAL PHYSIOLOGICAL METHOD 



consists therefore of two parts : a receiving bulb or tambour, and a recording 

 bulb or tambour. 



A very simple form of recording tambour is shown in Fig. 9. A hollow 

 aluminium tube (f) conveys the air- waves to the elastic membrane (b) fitting 

 over the chamber. A small metallic disk (c) is cemented to the membrane and 



on the upright bar as a fulcrum rests the writ- 

 ing lever (d}. The axle of the lever is held 

 in a yoke, the distance of which from the ful- 

 crum can be readily adjusted and the excur- 

 sions of the writing point be thereby varied 

 as desired. 



The second part of the apparatus or receiv- 

 ing tambour is usually in the form of a small 

 rubber balloon or of a small metallic box cov- 

 ered with a rubber membrane. The form of 

 the recording tambour can be the same for a 

 great many kinds of physiological movements, 

 but the form of the receiving tambour must be 

 adapted to the special form of experiment in 

 which it is being used. 



The receiver shown in Fig. 10 is adapted 

 for transmitting movements of the wall of the 

 carotid artery, for the purpose of securing a 

 pulse-tracing. It consists of a small metallic 

 box containing three small spiral springs, 

 which serve to give the membrane covering it 

 a certain tension. The membrane bears on its 

 outer side a small button or plunger which can 

 be applied to the skin over the artery. The 

 pulsatory movements of the arterial wall are 

 taken up by the plunger and are conveyed by the tube leading from the chamber 

 of the box to the recording tambour. The whole apparatus is fastened to the 

 neck by means of the hoop and screw. 



With well-constructed apparatus this method of registration has been found 

 to be very exact. But not all tambours are so constructed, and it is necessary 

 before undertaking any exact determinations to prove the apparatus. A very 



FIG. 10. Receiving tambour adapt- 

 ed for taking a pulse-record from 

 the carotid artery of man. 



FIG. 11. Pulse curve from the carotid artery of man, after Edgren. To be read from left to 



right. 



good test for a recording tambour is that of registering a pulse curve, the pulse- 

 beat being received from the carotid artery by an apparatus of given form. 

 With the receiver shown in Fig. 10 the tracing given by the carotid should be 

 essentially like that shown in Fig. 11. 



