450 THE HUMAN MOTOR 



Gaseous exchanges per hour: 565-3 litres, CO 2 2-55%, O 2 3% 

 CO* = .855. 



Consumption of oxygen per hour -- ^ = 16-96 litres. 



After a recitation at such a voice as to be clearly audible at a 

 distance of 6 metres from the speaker in a room of 250 cubic 

 metres capacity, the subject reciting at an average speed of 150 

 syllables per minute while seated motionless in a chair the results 

 obtained were as follows : 



Gaseous exchanges per hour : 799-5 litres CO 2 3-1% O 2 3-6% 



2 



= -86 

 " 



799-5 X 3-6 



Consumption of oxygen per hour- - 28-78 litres. 



1UU 



The gaseous exchange s in both cases are reduced to OC and 

 760 mm. barometric pressure 



The expenditure of energy in phonation Was therefore : 28-78 

 16-96 = 11-82 litres of oxygen, equivalent to 11-82 X 4-9 = 57-92 

 Great Calories per hour. 



It is known that a man who climbs a mountain quickly, expends 

 4 Caloiies per 425 kilogr?mmetres effected (an average yield of 

 25%). The equivalent in work done in lecturing in a loud voice 

 for an hour, and without other movements will be : 



K7.QO 



- X 425 = 6,154 kilogrammetres. 



equivalent to an ascent of a 100 metres up a mountain, at a speed 

 of 100 metres an hour. 



It must be pointed out, however, that the orator, the singer, 

 and the actor make numerous muscular movements and gestures 

 whose energetic equivalent must be added to the preceding ex- 

 penditure. To produce expression the artist brings into play 

 his limbs and muscles, so that the work of phonation is 

 inappreciable in comparison with all this muscular activity. 



Speaking causes a perceptible increase both in the frequency 

 of the respirations and also in the depth of the inspirations and 

 expirations, the former are more prolonged than the latter, in a 

 ratio of about 2 to 1 (vide fig. 308). It will be observed that 

 respiratory curves are unequal and irregular, and it would seem 

 that during speaking the thoracic enlargement is maintained and 

 diminishes but slightly, the expirations being brief. 



340. Intellectual Work. It has already been stated that 

 Atwater, after numerous experiments, coulcl not find tha^ the; 



