CHAP. IX.] THE CONTRACTILE TISSUES. 307 



The air was analysed by absorbing the carbon dioxide with caustic 

 solutions and the oxygen with phosphorus. He found that muscle, 

 whether at rest or in contraction, caused a diminution of oxygen and 

 an increase of carbon dioxide, and usually of nitrogen also, in the sur- 

 rounding air changes which were greater during contraction than 

 during repose of the muscle. The oxygen absorbed was greater than 

 the carbon dioxide exhaled. He exposed muscles to a vacuum, then 

 to pure hydrogen for two or three hours, then to an exhausted receiver, 

 which was subsequently filled with pure hydrogen. Notwithstanding 

 this careful removal of oxygen from about the muscles, carbon dioxide 

 was yielded up by them, especially on stimulation. Hence Matteucci 

 concluded that the oxygen which, in muscular respiration, helps to 

 form the carbon dioxide is not the oxygen of the air, but oxygen 

 which exists in muscle in a state of chemical combination 1 . 



Valentin ^ n 1857 Valentin published researches on the effect 



of contracting frog-muscles upon the atmosphere 2 . His 

 apparatus consisted of a glass cylinder, abed, 2 decimetres high and be- 

 tween 2 and 3 centimetres bore. The bottom was closed by an iron 

 plate,/, with a hook, e, externally for the attachment of a battery wire. 

 The top was provided with a short iron flange, gh, which supported an 

 iron plate or lid, ik, capable of being hermetically fixed to the cylinder 

 by means of an interposed washer and screws. This lid was provided 

 with an exit-pipe, x, guarded by a stopcock, as well as with a ther- 

 mometer, I, and a gauge, nrt, open to the air, all being securely fixed 

 in an air-tight fashion. 



In order to determine exactly the volume of air in the cylinder after 

 everything had been arranged for an experiment, the following preliminary 

 calculations were made. 



Let w = cubic contents of the glass cylinder and the proximal limb 

 of the gauge when all is screwed up and the gauge stands at zero (or. 

 Fig. 58). 



Let h be the height of mercury which must be poured into the distal 

 limb of the gauge to raise the mercury in the proximal limb up to o : i. e. 

 to diminish the volume v by the volume between q and o, or p. 



Then, if b equals the barometric pressure, it follows that 



v : (v - fj) = (b + h) : b, 



b + h 

 fA " h ' 

 b 



Now suppose that a volume, p, of mercury be poured into the glass cylinder 

 to the level vw, before the lid is screwed up ; and let the gauge again stand 



1 Matteucci, Op. cit. p, 138. 



2 G. Valentin, "Die Wirkung der zusammengezogenen Muskeln auf die sie um- 

 gebenden Luftmassen." Arch. f. physiol. Heilkunde. New Series, Vol. i. 1857, p. 

 283. 



