CHAP. X. §. IT. DUKING MUSCULAB CONTBACTION. 129 



contained in the other phial in which the frogs were 

 left in repose. It is almost superfluous to add, that 

 I made the complete analysis of the air in contact 

 with the frogs according to the methods generally 

 employed." He calls the phenomenon, ' muscular 

 respiration,' and states, that " a muscle which con- 

 tracts, absorbs, while in contraction, a much greater 

 quantity of oxygen, and exhales a much greater 

 quantity of carbonic acid and azote, than does the 

 same muscle in a state of repose. A part of the 

 carbonic acid exhales in the air, the muscle imbibes 

 the other part, which puts a stop to successive 

 respiration, and produces asphyxy of the muscle. 

 Thus a muscle even ceases to contract under the 

 influence of an electro-magnetic machine enclosed 

 in a small space of air : this cessation takes place 

 after a longer interval of time if the muscle is in the 

 open air, and much more slowly still if there be a 

 solution of potash at the bottom of the recipient in 

 vdiich the muscle is suspended. Muscles which have 

 been kept long in vacuum or in hydrogen are never- 

 theless capable, though in a less degree, of exhaling 

 carbonic acid while in contraction; this proves clearly, 

 that the oxygen which furnishes the carbonic acid 

 exists in the muscle in a state of combination." 



That different gases present great differences in 

 their influence upon the irritability of the muscular 

 tissue, and consequently over contraction, has been 

 long known. 



