RESPIRATION. 



265 



circumstances, the degree of contraction or dilatation of the lungs is 

 dependent on that of the boundary walls of the chest, the outer surface 

 of the one being in close contact with the inner surface of the other, 

 and obliged to follow it in all its movements. 



Methods of recording Respiratory Movements. 



The movements of respiration may be recorded graphically in several ways. 

 The ordinary method is to introduce a tube into the trachea of an animal, and 

 to connect this tube by some gutta-percha tubing with a T piece introduced 

 into the cork of a large- sized bottle, the other end of the T having attached to 

 it a second piece of tubing, which can remain open or can be partially or 

 completely closed by means of a screw clamp. Into the cork is inserted a sec- 

 ond piece of glass tubing connected with a Marey's tambour by suitable tubing. 

 This second tube communicates any alteration of the pressure in the bottle of 



Fig. 212. Stethograph or Pneumograph. h, tambour fixed at right angles to plate of steel f; 

 c and d, nrms by which instrument is attached to chest by belt e. When the chest expands, the 

 arms are pulled asunder, which bends the steel plate, and the tambour is affected by the pressure 

 of b which is attached to it on the one hand, and to the upright in connection with horizontal screw 

 g. (Modified from Marey's instrument.) 



the tambour, and this may be made to write on a recording surface (fig. 

 173). If the tube attached to the T piece be closed the movements of inspira- 

 tion and expiration are larger than if it were closed. The alteration of the 

 pressure within the lungs on inspiration and expiration is shown by the move- 

 ment of the column of air in the trachea. By these means a record of the 

 respiratory movements may be obtained. 



Various instruments for recording the movements of the chest by applica- 

 tion of apparatus to the exterior. Such is the stethometer of Burton Sander- 

 son. This consists of a frame formed of two parallel steel bars joined by a 

 third at one end. At the free end of the bars is attached a leather strap, by 

 means of which the apparatus may be suspended from the neck. Attached to 

 the inner end of one bar is a tambour and ivory button, to the end of the 

 other an ivory button. When in use, the apparatus is suspended with the 

 transverse bar posteriorly, the button of the tambour is placed on the part of 

 the chest the movement of which it is desired to record, and the other button 



