540 GRAPHIC RECORDS OF RESPIRATION. [BOOK n. 



FIG. 71. APPARATUS FOR TAKING TRACINGS OF THE MOVEMENTS OF THE 

 COLUMN OF AIR IN EESPIRATION. 



The recording apparatus shewn is the ordinary cylinder recording apparatus. 

 rThe cylinder A covered with smoked paper is by means of the friction-plate B put 

 into revolution by the spring clock-work in C regulated by Foucault's regulator D. 

 By means of the screw E, the cylinder can be raised or lowered, and by means of 

 the screw F its speed may be increased or diminished. 



The tracheotomy tube t fixed in the trachea of an animal is connected by india- 

 rubber tubing a with a glass T piece inserted into the large jar G. From the other 

 end of the T piece proceeds a second piece of tubing b, the end of which can be either 

 closed or partially obstructed at pleasure by means of the screw clamp c. From the 

 jar proceeds a third piece of tubing d, connected with a Marey's tambour ra (see 

 Fig. 37), the lever of which I writes on the recording surface. When the tube 

 b is open the animal breathes freely through this, and the movements in the air of 

 G and consequently in the tambour are slight. On closing the clamp c, the animal 

 breathes only the air contained in the jar, and the movements of the lever of the 

 tambour become consequently much more marked. 



Below the lever is seen a small time-marker n connected with an electro-magnet, 

 the current through which coming from a battery by the wires x and y is made and 

 broken by a clock-work or metronome. 



If, a receiver being used, the open end of the | be closed, the 

 animal breathes into and out of the receiver, and the movements of 

 the tambour are greatly increased. This has the disadvantage that 

 the air in the receiver soon becomes unfit for further respiration. 

 A similar increase of the movements of the lever of the tambour 

 may be obtained by connecting a piece of india-rubber tubing to the 

 open end of the | . By increasing the length of this tube, or slightly 

 constricting it, the movements of the lever may be increased without 

 very seriously interfering with the breathing of the animal. 



In another method the movements of the chest are recorded. When 

 a small animal such as a rabbit is used, the whole animal may be 

 placed in an air-tight box, breathing being carried on by means of a 

 tube inserted into the trachea and carried through an air-tight orifice 

 in the wall of the box. By another orifice and tube the air in the box 

 is brought into connection with a tambour, which accordingly registers 

 the changes of pressure in the air of the box produced by the move- 

 ments of the chest (and body) and thus indirectly the movements of 

 the chest. In man and larger animals the changes in the girth of the 

 chest may be conveniently recorded by means of Marey's pneumograph. 

 This consists of a hollow elastic cylinder, or a cylinder with elastic 

 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 



