20 8 



THE TIME RELATIONS OF RESPIRATORY MOVEMENTS. 



trace respiratory curves (pneumatograms) by means of recording in- 

 struments. 



Method. The graphic method can be applied in three different ways : i . The 

 representation of the range of motion in the individual parts of the thorax may 

 be obtained in the following manner: 



(a) K. Vierordt and Ludwig arranged an instrument in which the movement 

 of a definite part of the thorax was communicated to a lever, whose longer arm 

 traced the curve on a rotating drum. In like manner Riegel constructed his 

 double stethograph on the principle of the lever. It consisted of two levers on 

 the same support, arranged for use on a patient in such way that one lever was 

 applied to a certain spot on the healthy side of the chest, and the other lever 

 to the corresponding spot on the affected side. A sphygmograph may be em- 

 ployed for recording the respiratory curve, the instrument being placed free outside 

 of the chest upon a stand and applied in such manner that only the pad of the 

 elastic stylus touches the chest-wall at one point. J. Rosenthal constructed a 

 lever to register the movements of the diaphragm in animals (phrenograph) ; it 



FIG. 77. A, Brondgeest's Air-cushion for Recording the Respiratory Curves. B, A Respiratory Curve of a Healthy 

 Individual, Recorded on a Plate Attached to a Vibrating Tuning-fork (i vibration = 0.01613 sec.), to Deter- 

 mine the Time-relations. 



was inserted through an opening in the abdomen, and rested against the dia- 

 phragm. 



(b) The air-cushion of Brondgeest's pan sphygmograph (Fig. 77, A) is con- 

 structed on the principle of air-transference. This instrument consists of a saucer- 

 shaped brass vessel (a), over which is stretched a double-layered rubber mem- 

 brane (b c) . Between the layers of this covering there is enough air to make the 

 outer membrane bulge. This cushion is placed on a certain part of the thorax, 

 and fastened with bands (d d) that pass around the chest. Every enlargement 

 of the thorax presses against the membrane c, producing a diminution of the air- 

 space within the capsule. The latter is connected by means of the tube S with 

 the recording chamber that is pictured in Fig. 44 . 



Instead of this capsular arrangement, Marey, in the construction of his pneu- 

 mograph, uses a piece of thick, cylindrical, elastic rubber tubing. This is fastened 

 by bands like a girdle around the chest, and is connected by a tube with the 

 recording drum. 



2. The variations in the volume of the chest or in the exchanged respiratory 

 gases may be graphically recorded as follows: 



For this purpose E. Hering places an animal in an air-tight, closed chamber, 



