372 'RESPIRATION' OF CONTRACTING MUSCLES. [BOOK i. 



probably not effected by haemoglobin but by the tissue juices ; for 

 many invertebrates have no hemoglobin which yet have muscles 

 not essentially different from those of the frog. It may be simply 

 that the presence of oxygen assists the escape of the deleterious 

 carbon dioxide better than hydrogen or nitrogen, as was found 

 to be the case with the gases of the blood by Ludwig 1 . 



It may, therefore, be said respecting the oxygen of the surrounding 

 medium, that while an appreciable amount is abstracted and absorbed 

 in the inevitable putrefaction of exposed muscle, a small portion, 

 altogether too slight to affect a gas-analysis, is taken up to preserve 

 irritability. 



Resting The atmosphere surrounding exposed muscles, 



muscles ex- besides losing oxygen, suffers an increase of its carbon 

 hale C0 2 . dioxide. As was pointed out by Valentin, this is 



not wholly an exchange of a functional character ; but is common to 

 living and dead muscular tissue. In other words, it is one of the 

 early phenomena of putrefaction, together with the absorption of 

 oxygen. But a comparison of the exhalations of living muscle 

 and of muscle made rigid, discloses that less carbon dioxide escapes 

 from the normal, on mere exposure, than from the rigid. Since 

 putrefaction is more, and not less, rapid in normal muscle than in 

 muscle made rigid by heat (the method of inducing rigor usually 

 adopted in these experiments), it is clear that putrefactive changes 

 cannot be called in to explain this difference. There can be little 

 doubt that it is due to the increased amount of carbon dioxide which 

 rigor is known to generate in muscle (vide supra). The amount 

 of carbon dioxide given off is very irregular and has no relation 

 to the oxygen at the same time absorbed. 



-Hitherto we have considered the case of muscles 

 m re P ose ; an d we have come to the conclusion that, 

 sorb more o apart from an inappreciable quantity of oxygen, ab- 

 and exhale sorbed or otherwise employed, the exchanges of 

 more co 2 than ^he 'respiration' of exposed muscle are not func- 

 muscies tional, but putrefactive, and are shared alike by muscle, 



skin and other tissues. When we turn to the case 

 of muscles in tetanus we find that the gaseous exchanges have 

 a greater value, and especially as regards the carbon dioxide 

 excreted. The increase in the amount of oxygen absorbed is 

 indeed slight, and is due to the agitation of the tissue during 

 tetanus; for if the air about an unstimulated muscle be mechanically 

 kept in motion, a similar increase of the oxygen absorbed is found to 

 occur. It is not due to any increased activity of the putrefactive 

 processes brought about in the passage of the electrical currents, since 

 such currents have no influence over the putrefactive absorption of 

 oxygen by rigid muscles. The more remarkable increase of the carbon 



1 Hermann, Op. cit. p. 52. 



