3 20 THE POPULAR SCIENCE MONTHLY. 



that muscles deprived of their natural innervation could be kept tit 

 for work provided they were electrically excited at sufficiently brief 

 intervals ; an experiment which found an important application in 

 surgery and neuropathology. 



Even in the midst of health unused muscles pine away, or become 

 pale and powerless, like the ear-muscles of most men. In general, the 

 redness of muscles is related to greater strength in consequence of fre- 

 quent exertions. Herr Ranvier showed that the red and pale muscles 

 occurred together in rabbits and rooks ; that they were distinguished 

 by their structure and by the time required for contraction without its 

 being possible to decide that one set worked more than the other, and 

 without any clew being given to the object of this disposition. Little 

 is known of the microscopic qualities of used and unused muscles. In 

 contrast with the muscles of fattening cattle, working cattle have 

 thicker primitive bundles and coarser sarcolemma, the latter determin- 

 ing the lesser nutritive value of the flesh. According to Herr Vir- 

 chow's terminology, nutritive stimulation has also taken place. In 

 muscles falling away through disuse, as the waste progresses a fatty 

 metamorphosis sets in, against which, as is well known, its ceaseless 

 activity does not protect the heart-muscle. Muscular contraction is 

 accompanied by chemical changes. The blood flows darker from tense 

 than from resting muscles ; they consume more oxygen and form more 

 carbonic acid. An acid permanently reddening litmus is set free in 

 them. Their watery constituents and the amount of substances soluble 

 in alcohol increase in them, while the amount of substances soluble in 

 water diminishes probably because glycogen is consumed in the con- 

 traction. The albuminous constituents remain about the same, yet the 

 derivatives of albumen known as the flesh bases appear to be richer. 

 That to the last hard-working muscle, the heart, is for this reason a mine 

 of such bodies to the chemist ; and the flesh of a fox that had been 

 shot was found by Liebig to be ten times richer in creatine than that of 

 a captive fox. We are, unfortunately, still very far from understand- 

 ing the connection of these various processes and their relation to mus- 

 cular contraction, that is, to the interchange of isotropic and uniso- 

 tropic substances in the muscular fibers, and to the transformation of 

 mechanical, thermic, and electric forces. We only know that there is 

 involved an increase and modification of a process of change that was 

 already going on during rest, particularly of the oxidation of nitrogen- 

 ous substances, by which, in addition to mechanical labor-service, an 

 apparent surplus of heat is developed. Even the muscles at rest are a 

 seat of respiration and the development of heat in animal bodies. The 

 muscle acts very much like the reserve-locomotive that stands ready 

 for use on the switch, which is all the time burning a little fuel and 

 can be attached to a train or sent to help a disabled engine at any 

 instant, but which requires, in connection with the greater display of 

 force it is to make, a greater consumption of material and expenditure 



