380 PRESERVATION OF MUSCULAR IRRITABILITY. [BOOK I. 



part at least, accounted for by the greater rapidity of blood current 

 which then occurs. 



This is only true tinder the conditions of Ludwig and Schmidt's 

 experiments, in which an increased flow of blood through the muscle was 

 probably due to the blood being driven over a wider capillary area. More 

 O was taken up under the circumstances because more muscular substance 

 was brought to act upon the blood. It does not imply that the assumption 

 of O is dependent upon the rapidity of the blood stream, which is expressly 

 denied by Pfliiger 1 and Tinkler 2 . 



1). The more oxygen is contained in the blood flowing through 

 muscle, the greater is the ease with which the muscle takes up oxygen 

 from the blood. 



c. The amount of oxygen consumed by muscle in activity, or 

 by muscle exhausted by doing work, is usually perceptibly greater than 

 that consumed during rest. But the oxygen consumed bears no 

 definite relation to the work done. 



3. As regards the carbon dioxide excreted : 



a. In most cases, but not in all, the venous blood flowing 

 from contracting or exhausted muscle contains an increased amount 

 of carbon dioxide. The exact cause of the less usual condition, in 

 which the carbon dioxide of the blood is diminished, is not clear. 



6. The relationship between the carbon dioxide excreted and 



, , , .j 00 9 excreted . xl 



the oxygen absorbed, or the quotient ^ 2 , , , , in these 



experiments underwent no constant variation as the muscle passed from 

 the resting to the active condition. 



Dependence The value of oxygen in preserving the irritability of 



of muscular excised mammalian muscles may be readily demonstra- 

 irritabiiity ted. The circulation of a stream of oxygenated blood 

 upon a supply through muscle prolongs its life 17 or 20 hours beyond 

 the time when it would have died if left bloodless. 

 Hence Ludwig and Schmidt 3 concluded, in opposition to the doctrine 

 then current, that a peculiar respiration goes on within muscle which 

 proceeds independently of the so-called vital properties of the con- 

 tractile matter. Furthermore, irritability may not only be preserved 

 in muscle by means of oxygenated blood, it may also be restored after 

 it has become lost by exhaustion of the tissue. For the purposes of 

 such restoration of muscle extremely minute quantities of oxygen are 

 sufficient. In one experiment, when a muscle had completely lost its 

 irritability owing to the interruption of its blood current for 128 

 minutes, and when for 38 minutes more a stream of reduced blood 

 had been let flow through the muscle without beneficial effect, the 

 passage of 13'5 c.c. of arterialized blood through it, occupying the 



1 Pfliiger, " Ueber die Diffusion des Sauerstoffs, den Ort und die Gesetze der Oxida- 

 tionsprocesse im thierischen Organismus. " Pfliiger's Arch. Vol. vi. p. 48. 



2 Tinkler, " Ueber den Einfluss der Stromungsgeschwindigkeit und Menge des Blutes 

 auf die thierische Verbrennung." Pfliiger's Arch. Vol. x. p. 368. 



3 Op. cit. p. 46. 



