PHYSIOLOGY OF MOVEMENT. 



709 



the amount of CO 2 in muscles capable of withdrawal by the air-pump 

 amounting to 12.08 per cent, by volume of the muscle. The other con- 

 stituents of the muscle are represented in the following table (Charles) : 



ANALYSES OP MUSCLE. 



The constituents of muscle are, therefore, nitrogenous, non-nitroge- 

 nous, and inorganic. Under the former group occur myosin, alkali 

 albuminate, and serum-albumen, with extractives such as kreatin, sarkosin, 

 sarkin, xanthin, and carnin. 



Of the non-nitrogenous bodies, inosite, fat, and glycogen are the most 

 important, while phosphoric acid, potassium, sodium, magnesium, and 

 lime are the principal inorganic constituents. 



(b) Muscular Irritability. The principal physiological difference 

 between living and dead muscle is that the former, under the action of 

 various stimuli, is thrown into contraction. This property of contraction 

 results from what is termed irritability of the muscle. 



If the spinal cord and brain of a frog be destroyed the animal remains 

 perfectly passive, without any contraction occurring in any of its muscles. 

 If, however, an}' stimulus, mechanical, electrical, or thermal, be applied to 

 its muscles they at once shorten, and it is only on the onset of rigor 

 mortis that this power disappears. If the stimulus be applied to a motor 

 nerve-trunk a similar state of contraction is produced. 



In the destruction of the central nervous system the peripheral 

 nerve-branches have, of course, not been destroyed, and yet the contrac- 

 tility of muscle is not dependent upon the stimulation of nerve-fibres 

 distributed to it, for muscle, like other forms of protoplasm, possesses 

 an independent excitability. This may be demonstrated by a number of 

 different methods. In the first place, various chemical stimuli, such as 

 ammonia^ lime-water, etc., do not produce muscular contraction when 

 applied to motor nerves, but do evoke contraction when directly applied 

 to muscle. Again, in various muscles it is impossible to recognize the 



