356 GASES LIBERATED IN CONTRACTION OF MUSCLE. [BOOK I. 



stimulated in a vessel of air. The method of the experiments is to 

 take a preparation of frog-muscles and expose it before, during, and 

 after tetanus under exactly identical conditions, collecting the yield of 

 gases separately, for comparison. For this purpose the pelves and 

 hinder extremities of three or four frogs divested of their skins may be 

 arranged to form a chain attached at each end to a platinum electrode 

 of the boiling-flask/. At the bottom of this flask is a little normal 

 salt-solution to keep the atmosphere moist ; salt-solution being pre- 

 ferred to water in order to defend the preparation from injury during 

 the accidental spurtings of the fluid. The temperature of the boiling- 

 flask is carefully maintained constant throughout the experiment, 

 at about 16 20 C. The muscles are first exposed to a vacuum for an 

 hour and the gases (A) collected. They are then tetanized at intervals 

 during another hour and the gases (B) again collected, care being 

 taken not to force tetanus into rigor. And lastly, they are again 

 allowed to rest for an hour while the escaping gases (C) are a third 

 time collected. On analysis it appears that 



A contains the least amount of CO 2 . 

 B the greatest 

 C somewhat less than B. 



B and C may each contain more than three times as much carbon 

 dioxide as A ; and C may contain more than B, if, from any cause, 

 rigor happen during the third hour \ 



Thus in tetanus, as in rigor, the gaseous changes consist in an in- 

 crease of the carbonic anhydride capable of withdrawal by an air-pump. 

 The increase is due to a special production of the dioxide within the 

 muscle, and not to the decomposition of some pre-existent stable 

 form of it, by means of the acid which appears during tetanus. This 

 is demonstrated by comparing the gases of normal and tetanized 

 muscles from the same animal an experiment which is practicable 

 from the circumstance that muscles when tetanized in the cold 

 lose a very small quantity of gases 2 . Frogs are taken and buried 

 in snow until almost rigid. Their vessels are then washed out with 

 ice-cold salt-solution ; and one leg from each is amputated and 

 scalded in the manner already described : if the scalding has been 

 perfectly done the reaction of the muscle to litmus paper is neutral, 

 not acid. The scalded limbs are minced in a vessel kept cold over 

 a freezing mixture, and put into the boiling-flask with (unboiled) 

 salt-solution at 0. Phosphoric acid is placed in the froth-chamber v 

 ready for use. The minced muscle is evacuated at 50 ; then acidi- 

 fied, and again evacuated. Meanwhile the rest of the cold carcases 

 are arranged in series on a cold plate and tetanized at intervals 

 during many hours. At the end of this time these muscles also 

 are scalded : they should have an acid reaction. They are minced 



1 Hermann, Op. cit. pp. 116, 117. Expt. 11 and 12. 



2 Hermann, Op. cit. p. 25. 





