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



the atmospheric pressure, together with the muscle, and usually a little 

 moisture floating on the surface of the mercury ; while the muscle 

 was kept within reach by means of the attached wire. If stimulation 

 of the muscle were desired, it is easy to see how it would he ac- 

 complished. At the close of the experiment the muscle was dragged 

 down through the mercury, an operation which was found to be 

 attended by no loss of gases whatever. The gases left in the 

 tube were then passed into several dry absorption tubes in succession, 

 in order to get rid of the moisture on the surface of the mercury; 

 and finally they were ready for analysis. The carbon dioxide was 

 directly absorbed by caustics; the oxygen was exploded, and the 

 nitrogen read off. The oxygen of the original air was estimated from 

 the nitrogen left behind. All deviations from this in the final 

 analysis were considered to be due to the absorption of oxygen by 

 the muscles during the experiment. The method is open to three 

 trivial objections: The small amount of carbon dioxide normally 

 present in the air (4 parts in 10,000) is neglected; the atmosphere 

 is not absolutely constant in its composition as regards oxygen and 

 nitrogen ; muscle itself yields up nitrogen on exposure, but only in 

 excessively small amounts, and during the earlier parts of an ex- 

 periment (Hermann). 



Resting In this apparatus, by comparing during 15 or 20 



muscles hours the gaseous exchanges of bloodless muscles, some 



absorb 0. o f w hich were rigid while others were still living, it 



appeared that the absorption of oxygen is practically equal in the case 

 of both living and rigid muscles ; and therefore is probably not con- 

 nected with the functional mechanisms of the tissue. It is, in short, 



Absorption dependent upon a process of putrefaction which is accele- 

 of o is in part rated according to the extent of muscular surface exposed 

 I utref active. to the action of the air, and which begins at a very early 

 period of exposure. 



And in part But while the absorption of oxygen, as determined 



physiological, by an analysis of the surrounding gaseous medium, can- 

 not be ascribed to any but putrefactive causes, we must hasten to 

 explain that other and more delicate tests would lead us to infer an 

 extremely slight but constant employment of oxygen which is truly 

 physiological. 



Influence of ^- s ear lj as 1795 Humboldt 1 observed that muscles 



medium upon preserved their irritability longer in oxygen than in air 

 irritability of or gases containing no oxygen an observation which 

 muscle. h as s i n ce been confirmed by Georg Liebig 2 and others, 



and with especial accuracy by Prof. Hermann. In Hermann's 

 experiments a muscle was suspended in an absorption-tube by means 



1 Al. Humboldt, Versuche uber die gereizte Muskel- und Nerven-faser, 1797, Vol. n. 

 p. 282. 



2 Georg Liebig, Op. cit. 



