xin EESPIEATORY EHYTHM 483 



utmost by means of voluntary inhibition. On the contrary, he 

 tried as far as possible to eliminate this factor, turning his 

 attention away from the respiratory acts, so that they should be as 

 independent as possible of mental influences. 



The results of his researches differ from those above described, 

 inasmuch as the apnoeic period is followed not by a measure of 

 compensatory dyspnoea, but by the opposite phenomenon, i.e. an 

 increment in the inspirations similar to that exhibited by an animal 

 after the apuoea from artificial respiration with the bellows. 



FIG. '216. Compensatory dyspnoea, consequent on period of voluntary apnoea in mau. (Mosso.) 

 Tracing recorded with Marey's pneumograph. 



From his observations, as a whole, ISTeander draws the con- 

 clusion that the apnoea which he studied must be looked upon as a 

 combination of true and spurious apnoea. He found, in fact, that 

 its duration is in ratio with the percentage quantity of the oxygen 

 of the expired air. On the other hand, it starts as a spurious 

 apnoea deriving from fatigue of the centres, since a deep inspiration 



FIG. '217. Voluntary apnoea in man, preceded by four forced inspirations, and followed l>y a 



scarcely visible decrement. (Mosso.) 



of pure hydrogen equally determines a marked pause, although of 

 brief duration. The prolongation of the pause consequent on a. 

 series of deep inspirations must be considered as the effect of 

 greater central fatigue combined with diminished venosity of the 

 blood, which becomes normal again during the increment of the 

 succeeding respirations. 



XIV. Let us see if it is possible to obtain a true apnoea in 

 Miescher's sense by substituting gentle continuous ventilation of 

 the lungs for forced rhythmical ventilation, in order as far as 

 possible to avoid the mechanical excitation of the pulmonary 



