310 MECHANISM OF THE RESPIRATORY MOVEMENTS. 



Sandmann, 1 F. Franck, 2 Eiegel and Edinger, 3 Einthoven and Th. Beer. 

 Einthoven made use of two methods, both based on the increased resistance 

 to the passage of air through the bronchioles which would be occasioned by 

 contraction of the bronchial muscles. In the first method, artificial respiration 

 was carried out, a constant volume of air being blown in and sucked out at each 

 respiration. Any diminution in the calibre of the bronchioles must increase 

 the resistance to the incoming current, and so cause a rise of pressure in the 

 tracheal tube. Instead of recording the variations of pressure throughout the 

 whole of each stroke of the pump, an arrangement was made use of, by means 

 of which the mercurial manometer was connected with the trachea only 

 for a brief space of time, during one part of the inspiratory phase. The 

 lever recording the excursions of the mercury in the manometer recorded 

 therefore an almost unbroken line during the experiment. Any increased 



resistance to the 

 current of air 

 raised the pres- 

 sure during the 

 whole inspiration, 

 and therefore dur- 

 ing the moment 

 at which the 

 manometer was 

 put into connec- 

 tion with the 

 tracheal tube. A 

 rise of the lever 

 was thus pro- 

 duced, which con- 

 tinued with each 

 stroke of the 



pump, until the 

 level uf the mer- 

 cury corresponded 

 with the true 

 pressure obtain- 

 ing at the moment 

 of connection, 

 during constric- 

 tion of the bronchioles. Einthoven calls this arrangement a " differential 

 manometer," since its principle is the same as that of Bernstein's differential 

 rheotome. 



In the second method, artificial respiration at a constant pressure is 

 made use of. Any change in the bronchioles will in tins case affect the 

 volume of air entering the lungs at each stroke of the pump, and can be 

 measured by recording the passive respiratory movements of the chest wall or 

 diaphragm. In both cases the animal must be curarised, so as to abolish 

 spontaneous respiratory movements. 



The influence of stimulation of the peripheral end of the 

 vagus. — If in a curarised animal the peripheral end of either vagus 

 be stimulated, the effect is invariably a constriction of the bronchioles. 

 This is rendered evident by a rise of the manometer lever, if Einthoven's first 

 method of observation be adopted (Fig. 179); or by a diminution of the 

 respiratory movements of the thoracic wall, if the second method be 



1 Arch./. Physiol., Leipzig, 1890. S. 252. 



2 Arch, de physiol. norm, etpath., Paris, 1889, tome i. p. f>38. 



3 Ztschr.f. klin. Med., Berlin, Bd. v. S. 413. 



Fig. 179. — Tracings of blood pressure (middle curve) and of intra- 

 tracheal pressure (upper curve), taken by Einthoven's "differential 

 manometer." Between Q & Q' the peripheral end of one vagus 

 was stimulated. Time marking = seconds. 



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