CHAP. IX.] THE CONTRACTILE TISSUES. 417 



that muscles which for some hours had been rigorously excluded 

 from contact with oxygen gas, were yet capable of yielding carbon 

 dioxide, especially when in the act of contraction ; and he had con- 

 cluded that the oxygen which in 'muscular respiration' forms the 

 carbon dioxide is not the oxygen of the air but oxygen which exists in 

 muscle in a state of chemical combination. The same circumstance 

 attracted the attention of Traube. In his view, oxygen enters muscle 

 from the blood and unites there in some loose chemical combination, 

 from which it is readily abstracted by the oxidizable bodies of the muscle 

 juices. Muscular substance reacts to oxygen and reducing substances 

 like indigo, cupric hydrate or the vinegar ferment, and its action is more 

 perfect and rapid at the higher temperatures. Complete deoxidation 

 of a muscular fibre brings with it death-rigor, while complete saturation 

 with oxygen implies a perfect irritability. 



Heidenn i "^ n ^ s manner the doctrine of muscle was begin- 



ning to assume its present outlines when Heidenhain 1 

 demonstrated that the heat and mechanical work produced in con- 

 traction are not complementary that, in short, they vary in a similar 

 although not quite identical manner, when subjected to the same con- 

 ditions of tension, etc. The hypothesis of J. R. Mayer that mechanical 

 work arises at the expense of heat in muscle, which many observers 

 had endeavoured to sustain, became finally untenable; and it was 

 now necessary to assume that the heat-evolving and work- evolving 

 processes of muscle were in some degree independent of one another^ 



At this point Hermann 2 began his well-known 



Hermann. , r / , , > p ^ 



examination ot muscular respiration, most 01 the 



results of which have already been presented to the reader. Although 

 it was granted that the oxygen made use of in the formation of 

 carbon dioxide was not taken from the blood at the moment of! 

 formation, but was rather stored up in muscle at some time beforehand, 

 yet it seems to have been assumed that the act of formation of carbon 

 dioxide was a true oxidation ; and for this reason it had been found 

 necessary to suppose the existence of some body with affinities for 

 oxygen intermediate between those of haemoglobin and the oxidizable 

 matters of muscle. The great and peculiar stability of this hypothetical 

 oxygen-carrier, which could, while easily parting with its oxygen to 

 the oxidizable portions of muscle in contraction, yet steadily resist the 

 action of a vacuum even at high temperatures, was however always 

 a point of great difficulty ; and, to avoid it, Hermann surmised that 

 the chemical operation in contracting muscle is not a true oxidation, 

 but rather the splitting up of some complex body with the formation 

 of simpler, more stable, substances. Such decompositions were already 

 known to be capable of yielding energy, and especially heat ; as, for 

 instance, when the complex molecule of sugar, in the process of 

 fermentation, splits up into alcohol, carbon dioxide, etc., without 

 the help of oxygen from the air. 



1 Heidenhain, Mechanische Lcistungen, etc. 



2 Hermann, Stoff'wechsel der Huskeln. 



a 27 



