236 APPENDIX 



metallic holder. Each tambour should have a set of levers of varying 

 lengths say, 10 cm., 20 cm., and 30 cm. Fig. 56, page 106, shows 

 one form of recording tambour. 



The receiving tambours must be constructed with a view to their 

 adaptation to each particular experiment. The receiving tambour 

 of the cardiograph (Fig. 88, Card.) should be of medium size and 

 should have the membrane stretched rather tightly. The stetho- 

 graphic receiver should be far more capacious, having perhaps twice 

 the linear dimensions of the cardiographic tambour, and the mem- 

 brane should be only moderately stretched. The recording tambour 

 should be of the largest size and should be fitted with a short lever. 



The sphygmographic receiver should be only about 2 cm. in 

 diameter. When used for the carotid pulse no membrane is used. 

 To trace the radial sphygmogram a membrane with a button is used 

 as described in the text. 



The plethysmographic receiver is used to determine the varying 

 size of the finger incident to circulatory changes. The finger is 

 inserted through the rubber collar. The record is made by the 

 smallest recording tambour. 



The cannular receiver is used for taking changes in intrathoracic 

 and intra-abdominal pressure. 



13. THE MANOMETER TAMBOUR. 



A very large number of research problems require the recording 

 blood pressure of the animal (rabbit or dog) under observation. In 

 the physiological or in pharmacological laboratories, where such ob- 

 servations are in progress almost daily, it is not difficult to get satis- 

 factory results with the classical apparatus, which consists of a mercury 

 manometer whose proximal tube (p) is joined through the medium 

 of the pressure tubing (Pt) to the cannula (0), the pressure tubing 

 being interposed at (T) by a T-tube, one limb of which passes to 

 the reservoir containing one-half solution of MgSO 4 or some other 

 agent for retarding coagulation. Into the distal limb of the manom- 

 eter (d) there is fitted, in the classical apparatus, a float which rests 

 on the mercury, following more or less accurately the variations in 

 the lever, and carrying a vertical rod which slides through a guide 

 in the upper end of the distal limb, and bears at its upper extremity 

 a horizontal reed, bearing at one end a tracing point. 



There are two serious difficulties with this float. First, it is likely 

 to fail to work properly just at the time when you are most anxious 

 that there should be no interruption in your observation, though if 

 the apparatus is in almost daily use this difficulty is not a serious 

 one. The serious objection against the float is that it does not follow 

 accurately the movement of the mercury. The mercury starts up 

 a little before the float does, and the float itself has so much inertia 



