RESPIRATION 93 



in the prone position with the head on one side. Kneel or squat by 

 the side of or across the lower part of the body, facing the head, and 

 place your hands flat on the loins with the thumbs nearly touching at 

 the spine (fig. 75). Throw the weight of your body forwards on the 

 hands, keeping your arms straight (^4), and count slowly one, two, three, 

 four, five. Whilst counting four, five, swing backwards (B) so as to take 

 the weight off your hands. Then swing forward again, counting, as 

 before, one, two, three, and backwards, counting four, five ; and so on 

 about twelve to fifteen times a minute. The effect of the pressure is 

 to force the abdomen and lower part of the chest against the ground 

 so that the viscera are pressed against the diaphragm. In this way 

 air is driven out of the lungs. On relaxing the pressure the parts 

 resume their former position ; the diaphragm descends and air is 

 drawn into the lungs. 



The amount of air thus pumped through the lungs in a minute can 

 be measured by the spirometer in the same way as the tidal air 

 measured in natural respiration. 



Negative pressure within thorax. Introduce through an intercostal space Into 

 the pleural cavity in the human cadaver or in any dead animal a sharp-pointed 

 cannula or hollow trochar connected by rubber tubing to a water manometer. 

 Notice that as soon as the trochar passes into the pleural space the water hi the 

 distal part of the manometer sinks and registers a certain amount of negative 

 pressure within the thorax. 



Effects of stimulation of nerves and of asphyxia upon the respiratory move- 

 ments of animals. These have been studied hi connexion with blood-pressure 

 (see pp. 81, 82). 



