On the different Forms of Breathing. 101 



found to be given out of the blood than can be accounted for by the 

 oxygen consumed, or, in other words, the volume of air expired 

 exceeds in a marked degree the volume of air inspired. Where can 

 the excess of C0 2 come from ? It is evidently due to an emission 

 from the blood of a portion of C0 2 stored up within it. This view 

 is advocated by C. Speck in his paper, which has been referred to in 

 my last communication. It will be shown presently that a further 

 and more direct proof of this interesting fact can be experimentally 

 given. 



Until tracings of the phenomenon had been obtained on the record- 

 ing drum, I thought the return to normal respiration was effected at 

 the point C in the diagram, assuming that from B to C the blood 

 recovered its C0 2 entirely and replenished its store ; but as soon as 

 tracings were obtained it became obvious that the final return to 

 normal breathing failed to take place at C, and that the influence of 

 the forced breathing continued to show itself as far as the point D. 



This influence may appear consistent with the observation of 

 C. Speck, who allies the "after stage" of forced breathing to the 

 " after stage " of breathing under exercise ; but the phenomenon 

 appears to me to be strictly a character of forced respiration, inas- 

 much as it begins with apncea, passing gradually into slightly 

 increased breathing. 



In the following table the C0 2 entered as expired in forced breathing 

 is the total C0 2 expired from A to D in the diagram, and includes, 

 therefore, the C0 2 expired in forced breathing plus the C0 2 emitted 

 in the stage of apnoea and that obtained in the final reaction from 

 C to D ; the whole volume being calculated per minute. 



It will be observed that the volumes of C0 2 in the experiments in 

 forced breathing (including after stage) invariably exceed the volumes 

 of C0 2 obtained in the same lapse of time during rest ; this excess, 

 which is entered in the table for each experiment, must represent the 

 work done per minute in forced breathing. 



The mean amount of this work done per minute would be equal to a 

 combustion yielding 62'5 c.c. C0 2 for the author, and 47'5 c.c. C0 2 for 

 Mr. Floris, corresponding to a consumption of carbon of 0'034 gram 

 per minute for the author and 0'025 gram per minute for Mr. Floris. 



The subject is further developed in the appendix to this paper. 



A great deal more C0 2 is expired in forced respiration indepen- 

 dently of the reaction and after stage than in ordinary breathing, and 

 I shall now beg to demonstrate experimentally that this excess of 

 expired C0 2 is from the store of absorbed C0 2 in the blood (with the 

 exception of the small proportion for work done) and not a product 

 of oxidation. 



In order to attain that object, air forcibly inhaled was expired 

 into three different bell-jars in succession, the air being diverted 



