FREQUENCY AND CHARACTER OF RESPIRATORY MOVEMENTS 473 



modeled after the sphygmograph. A very simple stethograph may be 

 made by applying an ordinary rubber bulb to the surface of the chest 

 by means of a tape and by connecting its orifice with a recording 

 tambour. Marey 1 has advocated the use of a rubber tube closed at 

 its ends and fastened around the chest. This tube is connected by 

 means of a cannula with a recording drum which then responds to 

 the changes in pressure caused by the respiratory movements. Later 

 on this pneumograph took the form of a metallic tambour placed 

 directly over a narrow plate of steel. When properly applied to the 

 surface of the chest, the respiratory movements subject this plate to 

 different degrees of tension which are transferred by a lever to the rub- 

 ber membrane of the tambour (Fig. 245). Another method fre- 

 quently practised is to register the variations in the intrapleural 

 pressure by means of a tambour connected with the intrapleural space. 

 In a similar way, the intrathoracic pressure may be recorded with the 

 help of a tambour connected with a catheter which is passed down the 



FIG. 245. DIAGRAM OF MAREY'S PNEUMOGRAPH. 



The instrument consists of a tambour (<), 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. (American Text-book of Physiology.) 



esophagus until its free end comes to lie a short distance above the dia- 

 phragm. It is also possible to insert a T tube in the trachea and to 

 connect its lateral branch with a recording tambour, or to permit the 

 animal to respire through a large bottle, one of the outlets of which 

 communicates with a recording instrument. If the abdomen has been 

 opened, the diaphragm may be connected with a writing lever by means 

 of a small hook and thread acting over a pulley. It has also been advo- 

 cated to separate the ensiform cartilage from the manubrium of the 

 sternum and to attach it by means of a thread to an ordinary writing 

 lever. 



Pneumatogram. A record of the respiratory movements consists 

 as a rule of a series of waves composed of alternate upstrokes and 

 downstrokes, but whether the inspiratory period is represented by the 

 ascending limb or by the descending limb depends upon the manner 

 of action of the recording instrument. Thus, Marey 's pneumograph 

 acts aspiratingly, pulling the lever of the recording tambour downward 



*La methods graphique, Paris, 1873; also see : Brondgeestsche, Onderzoek, 

 g. i. h. physiol. Lab., Utrecht, ii, 1873, 326. 



