FREQUENCY AND CHARACTER OF RESPIRATORY MOVEMENTS 485 



this difficulty in some measure, but this procedure cannot be resorted 

 to in human beings unless undertaken as a last means to save life. 

 The manual method of artificial respiration possesses the advan- 

 tage that it can be applied almost immediately. A delay of more 

 than ten minutes should never result, because it is practically impossi- 

 ble to restore life if this period of time is exceeded. Furthermore, it 

 is to be remembered that the body becomes entirely flaccid in the 



Fig. 251. — Device to Illustrate the Influence of the Respiratory Movements 

 UPON THE Flow of the Blood through the Pulmonary Blood-vessels. (Hering.) 

 A, bell jar; B, rubber membrane closing it; V, soft rubber pouch to imitate the 

 pulm. blood-vessels; GH, arrangement for forcing water through V under a constant 

 pressure; j, manometer connected with "intrapleural space." On inspiration, pro- 

 duced by moving the rubber membrane downward, the intrapleural pressure is de- 

 creased. This gives rise to an aspiration which tends to pull the wall of V outward, 

 facihtating the flow from G to H. 



course of ten or fifteen minutes,^ and that it is then practically impos- 

 sible to ventilate the lungs by means of pressure with the hands. Res- 

 piration not having been restored within this time, it is advisable 

 to resort to the method of inflation, but the apparatus should be placed 

 in the hands of a thoroughly experienced operator. 



It is a well-known fact that the arterial blood pressure rises during 

 inspiration and falls during expiration, while the venous pressure rises 



1 Liljestrand, Wollin and Nilsson, Skand. Archiv fiir Physiol., xxix, 1913, 198. 



