STRIATED MUSCLE. 73 



placed in an atmosphere containing oxygen. 1 In the living 

 animal, the venous blood which flows from the muscle differs 

 essentially from the arterial blood which enters it, having 

 less oxygen, and more carbonic acid. 



The respiration of a muscle is in direct proportion to its 

 life, and as the latter depends in a great measure on the 

 trophic (nutrient) influence of the nervous centres, if the 

 nerve of a muscle be cut, the gaseous exchange will be con- 

 siderably less., as well as the elasticity be diminished (see 

 preceding page). We explained the simultaneous modi- 

 fication in the chemical phenomena and the elasticity of the 

 muscle, by saying that its respiration is accelerated by its 

 tonicity / the meaning of which word we have already given. 



It should be added^ that the muscle, under form No. 1, is 

 alkaline ; under this form, no doubt, its chemical phenomena^ 

 are not sufficient to produce acids capable of neutralizing the 

 alkalinity of the blood contained in the muscle. 



Electro-motor Power. The muscle possesses electro-motor 

 properties, that is to say, it gives rise to electric currents ; 

 this may be proved by making the two wires of a galvanom- 

 eter communicate, one with the interior 

 part of a fnuscle, or transverse section, 

 the other with the outside of the same 

 muscle, or longitudinal section ; the 

 current flows always from the surface 

 to the centre ; that is, the surface, or 

 longitudinal section, is positive in re- 

 lation to the centre, or transverse sec- 

 tion (Fig. 19). 



Presuming that this electro-motor 

 power might furnish the key to the 

 principal properties of the muscle, especially to that by 

 which it passes from form No. 1 to that of No. 2 (for we 



1 Hermann (Berlin, 1867) maintains that the phenomena of 

 gaseous exchange presented by the muscles, when separated from 

 the body, and brought into contact with the air, are phenomena of 

 simple putrefaction. But Paul Bert has shown them to be really 

 phenomena of respiration, of life, and has proved the existence of 

 these respiratory exchanges, though in a less degree, in different 

 tissues. See " Lecons sur la Physiologic comparee de la Respira- 

 tion.' ' 1870. 4e Legon ; " Respiration des Tissus. ' ' 



* In the galvanoscopic circuit the current flows from a to ft, as indicated by 

 the arrows, o, Longitudinal surface of the muscle, positive (+). b t Section or 

 transverse surface negative ( ). 



