On the different Forms of Breathing. 105 



exercise, and then gradually returns to the normal. This " after 

 stage " of muscular exercise is attended with a feeling of breathless- 

 ness, due mainly to the C0 2 accumulated in the blood during exercise. 

 By increased expansion of the lungs, it soon finds its way into the 

 air inspired, and is thus removed from the blood. 



The tracing obtained on the chart for muscular exercise is steeper 

 than that for breathing in the state of repose ; on the person under 

 experiment assuming the recumbent posture in an armchair, the 

 tracing will be observed to be somewhat prolonged, then it straightens, 

 parallel with the tracing for breathing in repose. 



In none of these curves are there any signs of the reaction of 

 forced breathing. 



Muscular exercise of every kind, including singing, reading, talk- 

 ing, laughing, weeping, gives the same kind of tracing on the chart, 

 though of course more or less steep, as will be seen in the accom- 

 panying curves. But in such kinds of exercise as singing, reading, 

 talking, &c., which are not followed by breathlessness, it will be seen 

 that the curve is either not prolonged at all, or but very slightly 

 after the exercise is over, returning quickly to the normal; and 

 showing that in these cases the C0 2 is emitted as fast as it is formed, 

 or nearly so, little or none being detained in the blood. 



There are passive forms of exercise which also increase the volume 

 of air breathed and produce an excess of carbonic acid, such as 

 friction of the skin, and cutaneous irritation. On the author's bare 

 legs being rubbed hard by two persons, the volume of air he expired 

 increased per minute from 3'892 litres to 4'441 litres, and the volume 

 of C0 2 from 182'6 c.c. to 208'6 c.c. It may be therefore concluded 

 that " shampooing " is really a form of exercise, as it must be pro- 

 ductive of increased combustion. The application of a mustard leaf 

 to each leg, causing a powerful degree of smarting, gave rise to a 

 similar effect on the respiration ; the volume of air breathed was in- 

 creased per minute in one experiment from 4' 719 litres to 5*099 

 litres, and the C0 2 from 189'4 c.c. to 226'7 c.c. 



Breathing under the Influence of the Will. 



The fourth,form of breathing is while under the influence of the 

 will. It had occurred to me to inquire whether the will without 

 muscular exercise was attended with an increased volume of air 

 breathed and a simultaneous excess of C0 2 expired. The experi- 

 ment was carried out as follows. The person under experiment 

 rested for a while in the recumbent posture in the deck chair, and 

 then expired naturally into the bell-jar connected with the recording 

 instrument, thus a tracing of his normal breathing was obtained. 

 Then he commenced applying the will as he thought best, either to 



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