562 MUSCLES. 



become softer. This is in part produced by the strong acid dissolving 

 the myosin-clot and in part by autolytic processes (VoGEL). 1 



Metabolism in the Inactive and Active Muscles. It is admitted 

 by a number of prominent investigators, PFLUGER and COLASANTI, 

 ZUNTZ and Ro'HRiG, 2 and others, that the metabolism in the muscles is 

 regulated by the nervous system. When at rest, when there is no mechan- 

 ical exertion, there exists a condition which ZUNTZ and ROHRIG have 

 designated " chemical tonus." This tonus seems to be a reflex tonus, for 

 it may be reduced by discontinuing the connection between the muscles 

 and the central organ of the nervous system by cutting through the spinal 

 cord or the muscle-nerves. The possibility of reducing the chemical 

 tonus of the muscles in various ways offers an important means of decid- 

 ing the extent and kind of chemical processes going on in the muscles 

 when at rest. In comparative chemical investigation of the processes 

 in the active and the inactive muscles several methods of procedure have 

 been adopted. The same active and inactive muscles have been compared 

 after removal, also the arterial and venous muscle-blood in rest and activ- 

 ity, and lastly the total exchange of material, the receipts and expend- 

 itures of the organism, have been investigated under these two conditions. 



By investigations according to these several methods it was found 

 that the resting muscle takes up oxygen from the blood and returns to 

 it carbon dioxide, and also that the quantity of oxygen taken up is greater 

 than the oxygen contained in the carbon dioxide eliminated at the same 

 time. The muscle, therefore, holds in some form of combination a part 

 of the oxygen taken up while at rest. During activity the exchange of 

 material in the muscle, and therewith the exchange of gas, is increased. 

 The animal organism takes up much more oxygen in activity than when 

 at rest, and eliminates also considerably more carbon dioxide. The 

 quantity of oxygen which leaves the body as carbon dioxide during 

 activity is much larger than the quantity of oxygen taken up at the same 

 time; and the venous muscle-blood is poorer in oxygen and richer in 

 carbon dioxide during activity than during rest. The exchange of gases 

 in the muscles during activity is the reverse of that at rest, for the active 

 muscle gives up a quantity of carbon dioxide which does not correspond 

 to the quantity of oxygen taken up, but is considerably greater. It 

 follows from this that in muscular activity not only does oxidation take 

 place, but also splitting processes occur. This also results from the fact 

 that removed blood-free muscles when placed in an atmosphere devoid of 



1 R. Vogel, Unters. iiber Muskelsaft, Deutsch. Arch. f. klin. Med., 1902. 



2 See the works of Pfluger and his pupils in Pfliiger's Arch., 4, 12, 14, 16, and 18; 

 Rohrig, ibid., 4. See also Zuntz, ibid., 12. In regard to the metabolism after curare 

 poisoning, see also Frank and Voit, Zeitschr. f. Biologic, 42, and Frank and Geb- 

 hard, ibid., 43. 



