MECHANICAL PHENOMENA OP EXTERNAL RESPIRATION 233 



yielded results of importance in the study of normal respiratory con- 

 ditions, and still more important results in pulmonary disease. 



For most physiological purposes, however, a faithful graphic record 

 of the respiratory movements is indispensable. This may be obtained 



(1) By registering the movements 

 of a single point, or the variations in 

 a single circumference, of the bound- 

 ary of the thoracic cavity. In man 

 changes in the circumference of the 

 thorax at any level can be recorded 

 by means of a tambour adjusted to 

 the chest (Figs, in and 134), and in 

 communication with another, which 

 is provided with a writing lever 

 (Figs. 99 and 137). Or an elastic 

 tube, with a spiral spring in its 

 lumen, may be fastened around the 

 thorax or abdomen and connected 

 with a piston-recorder (a small cylin- 

 der in which works a piston carrying 

 a writing-point) (Fitz). 



(2) By recording the changes of 

 pressure produced in the air-passages 

 by the respiratory movements. This 

 can be done by connecting a cannula 

 in the trachea of an animal with a 

 recording tambour in the manner 

 described in the Practical Exercises 

 (p, 3oo). The variations of pressure 

 may be measured by connecting a 

 manometer with the trachea, or in 

 man with the nostril. 



(3) ; By writing off the changes of pressure which occur in the thoracic 

 cavity during respiration. For this purpose a trocar (Fig. 113) is intro- 

 duced through an intercostal space into one of the pleural sacs, without 

 the admission of air, or into the pericardium, and then connected with 

 a manometer or other recording apparatus. Or a tube, similar in con- 

 struction to a car- 

 diac sound (p. 96), 

 may be pushed 

 down the cesopha- 

 gu?. The varia- 

 tions in the intra- 

 thorrxic pressure 

 are transmitted to 

 the air in the elas- 

 tic bag, and thence 

 to a tambour. 



(4) In the rabbit 

 the part of the dia- 

 phragm attached to the ensiform cartilage may be isolated from the 

 rest and its contractions recorded by a lever (Head). For scone purposes 

 this is the best method. 



When the respiratory movements are studied in any of these ways, 

 it is found that there is practically no pause between the end of 



Fig. in. Scheme of Tambour for 

 recording Respiratory Movements. 

 C, a metal capsule connected airtight 

 with B, A, two caoutchouc mem- 

 branes, the chamber formed by which 

 can be inflated by means of the tube 

 and stopcock E. The tube D con- 

 nects the space H with a registering 

 tambour provided with a lever. The 

 membrane A is applied to the chest, 

 round which the inextensible strings 

 Fare tied. At every expansion of the 

 chest the pressure in H is increased, 

 and the increase of pressure is trans- 

 mitted to the registering tambour. 



Fig. ii2. Respiratory Tracing from Man (Marey). Down 

 stroke, inspiration; up stroke, expiration. 



