366 'RESPIRATION' OF EXCISED MUSCLES. [BOOK i. 



of mercury. On the top of the mercury in the tube, floated a 

 caustic solution to absorb the carbonic anhydride. A rise of the 

 surface of mercury betokened absorption of oxygen ; for Liebig paid 

 no regard to the nitrogen, and assumed that the oxygen and the 

 carbonic anhydride were interchanged volume for volume. He 

 stated that excised frog-muscles, whether bloodless or unbled, on 

 exposure to an atmosphere of common air or of oxygen, absorb oxygen 

 and excrete carbonic anhydride. He made out also that the excretion 

 of carbon dioxide may occur into an atmosphere containing no oxygen 1 . 



Valentin After Liebig, in 1855, Valentin 2 took up the same 



question of the influence of excised muscle on its 

 surrounding medium, with a view to discover differences of composition 

 between irritable and non-irritable muscle. The muscular hind limbs 

 of frogs were exposed to air in closed tubes for 1 6 days, and the air 

 examined at intervals. Irritability was abolished in various ways, as by 

 spontaneous death, by subjection to high temperatures, or by beating 

 to death ; and comparisons were established between the gaseous 

 exchanges of normal muscle, of non-irritable muscle, and of various 

 tissues, such as the skin and bones of the frog's body. He discovered that 

 other organs besides muscle abstract oxygen and excrete carbonic 

 anhydride; and, which was more important, that the gaseous exchanges 

 of muscle continue uninterruptedly after the death of the muscle. 

 In a word, not only living muscle, but skin and even dead muscle have 

 a 'respiration.' The gaseous exchanges of dead muscle are indeed 

 different from those of the yet living ; and the kind of exchange which 

 is characteristic of the dead state is established as soon as ever death 

 of the muscle intervenes, whether it be suddenly induced or whether 

 it be reached by a protracted decline. Active muscle does not 

 appreciably affect the nitrogen of the surrounding air; but after 

 irritability is lost, nitrogen escapes from the muscle. This difference 

 in the gaseous exchanges of the living and dead state was considered 

 by Valentin to betray some difference of constitution so subtle as 

 to escape chemical analysis or electrical tests. 



Matteucci ^ ne y ear ^ ater ' ^ n 185 ^> Matteucci published a paper 



in which the same subject of muscular respiration is 

 treated of 3 ; but especially the respiration of muscles during contraction. 

 He divested frogs of their skin, took the hinder extremities and freed 

 them roughly from blood with filter-paper, and arranged them in a 

 closed air-space over mercury, for electrical stimulation. The air-space 

 measured about 70 80 c.cm. Stimulation was carried on at intervals 

 so as not to fatigue the muscles. 



1 Op. dt. p. 408. 



2 G. Valentin, "Ueber die Wechselwirkung der Muskeln und der sie umgebenden 

 Atmosphere." Arch. f. physiol. Heilkunde, 14th year, 1855, p. 431. His methods of 

 analysis are explained in Valentin's treatise on Physiology. 



3 Ch. Matteucoi, "Recherches sur les phenomenes physiques et chimiques de la 

 contraction inusculaire." Ann. de cltimie et de physique, 3 s6rie, Vol. XLYII. 1856, 

 p. 129. 





