570 GRAPHIC RECORDS OF RESPIRATION. [BOOK n. 



ends, the interior of which is connected with a tambour. By means 

 of a strap attached to each end of the cylinder the instrument can be 

 buckled round the chest like a girdle. When the chest expands, the ends 

 of the cylinder are pulled out, and the air within the chamber rarefied; 

 in consequence the lever of the tambour connected with its interior is 

 depressed; conversely, when the chest contracts, the lever is elevated. 

 The pneumatograph of Fick is somewhat similar. Or changes in one 

 or other diameter of the chest may be recorded by what may be 

 called the 'callipers' method, as in the recording stethometer of 

 Burdon-Sanderson. This consists of a rectangular framework con- 

 structed of two rigid parallel bars joined at right angles to a cross 

 piece. The free ends of the bars, the distance between which can be 

 regulated at pleasure, are armed, the one with a tambour, the other 

 simply with an ivory button. The tambour bears on the metal plate 

 of its membrane (m Fig. 37) a small ivory button in place of the 

 lever. When it is desired to record the changes occurring in any 

 diameter of the chest, e.g. an antero-posterior diameter from a point in 

 the sternum to a point in the back, the instrument is made to encircle 

 the chest somewhat after the fashion of a pair of callipers, the ivory 

 button at one free end being placed on the spine of a vertebra behind 

 and the tambour at the other on the sternum in front in the line of the 

 diameter which is being studied. The distance between the free ends 

 of the instrument being carefully adjusted so that the button of the 

 tambour presses lightly on the sternum, any variations in the length 

 of the diameter in question will, since the framework of the tambour is 

 immobile, give rise to variations of pressure within the tambour. These 

 variations of the 'receiving' tambour as it is called are conveyed by a 

 flexible tube containing air to a second or 'recording' tambour, the 

 lever of which records the variations on a travelling surface. For the 

 purpose of measuring the extent of the movements the instrument 

 must be experimentally graduated. Other forms of callipers may of 

 course be used. 



By still another method the variations in intrathoracic pressure, 

 by means of which the movements of the chest walls produce the 

 movement of air in the lungs, may be recorded. This may be effected 

 by introducing carefully, to the total exclusion of air, into a pleural 

 cavity, or into the pericardial cavity, a cannula connected by a rigid 

 tube with a manometer. With each inspiration a negative pressure, 

 or rather an increase of the existing negative pressure, is produced, the 

 mercury, or fluid, in the manometer returning at each expiration. An 

 easier method of recording this intrathoracic pressure is to introduce 

 into the esophagus an elastic sound (similar to the cardiac sound, 

 Fig. 37) connected with a tambour. The O3sophagus within the thorax 

 like the heart and great vessels, as we shall see, is affected as well as 

 the lungs by the variations of intrathoracic pressure brought about by 

 the respiratory movements. 



In yet another method the movements of the diaphragm which, as 

 we shall see, serve as the prime agent in bringing about the enlarge- 

 ment of the thoracic cavity are recorded. This may be done by 

 inserting, through an incision in the abdominal wall, a flat elastic 

 bag between the diaphragm and abdominal organs. When in inspi- 



