EXTERNAL RESPIRATION AND RESPIRATORY MOVEMENTS. 599 



passages is recorded. In these methods a tube may be inserted into 

 one of the nostrils for instance, and then connected to a tambour the 

 lever of which makes its record on a kymographion, or if the animal 

 is tracheotomized a side tube upon the tracheal cannula may be 

 connected to a tambour. This method indicates well the rate of 

 movement and the relative amplitude, but has the defect that it 



Fig. 245. Figure of Marey'.s pneumograph. (Verdin.) The instrument consists of 

 a tambour (I), mounted on a flexible metal plate (p). By means of the bands c and c 

 the metal plate is tied to the chest. Any increase or decrease in the size of the chest will 

 then affect the tambour by the lever arrangement shown in the figure. These changes in 

 the tambour are transmitted through the tube r as pressure changes in the contained air 

 to a second tambour (not shown in the figure) which records them upon a smoked drum. 



does not record the pause, if any, at the end of inspiration or ex- 

 piration. A modification of this method that permits an accurate 

 record of the amplitude and duration of the movements consists in 

 connecting the trachea or nostrils with a large bottle of air. The 

 animal breathes into and out of the bottle, and the corresponding 



Fig. 246. Curve of normal respiratory movements. (Marey.) Curve A, full line, 

 represents the movements when the respiration is entirely normal. Downstroke, inspira- 

 tion; upstroke, expiration. CurveO, dotted line, represents the increased amplitude of the 

 movements, slight dyspnea, caused by breathing through a narrow tube. 



variations in pressure are recorded by a tambour also connected 

 with the interior of the bottle. (3) Methods in which the change 

 of pressure in the thoracic cavity is recorded. This end may be 

 reached by inserting a cannula into the thoracic wall so that its 

 opening lies in the pleural cavity, or, more simply, a catheter or 

 sound connected at the other end to a tambour may be passed down 



