CHAP. IX.] THE CONTRACTILE TISSUES. 353 



solution clinging to the frozen muscle, and which, becoming 

 disengaged, rise to the surface. This simple method is more 

 successful in preventing the intrusion of air-bubbles than that of 

 introducing the muscle into the boiling-flask under a surface of 

 mercury. When all the muscle has been introduced, the boiling-flask 

 is at once attached to the froth-chamber, the stopcock c being closed, 

 and the greatest care being taken not to include bubbles of air. 

 Salt-solution may be used either after shaking it up with the air of 

 the room, or after exhaustion of its dissolved gases by the air-pump; 

 in the former case it is necessary to ascertain the gaseous impurities 

 of the salt-solution and allow for them at the close of the experiment. 



If it is desired at any time during the experiment to treat the 

 muscle with acids, the acid must be carefully placed in the froth- 

 chamber v, before its neck g is attached to the pump. Meanwhile 

 the boiling-flask / is surrounded by a freezing mixture in the position 

 figured in B. 



It will be seen that the whole object of the experiment is to boil 

 a mixture of salt-solution and muscular tissue reduced to as fine a 

 state of division as possible; the preparation (which may occupy 

 about two hours) being made at a temperature least favourable to 

 spontaneous changes of the tissue to be analysed. 



The muscle having been lodged in the apparatus for collecting the 

 gases, all that is necessary is to induce rigor ; and this may most readily 

 be done by raising the temperature of the boiling-flask. The froth- 

 chamber v is then made vacuous and the gases which boil over are 

 passed through the pump into the absorption-tube for analysis. At a 

 temperature of C. little or no gas is given off, and then only after 

 several hours exposure. As the temperature rises to 15C. there 

 is an indefinite, dribbling discharge. At temperatures beyond this, 

 up to 30 C., there is at first a large escape of gas which afterwards 

 subsides. But it is at still higher temperatures, of 40 50 C., 

 that the greatest discharge occurs; here, also, it is voluminous 

 at first, becoming less and less as the exposure continues. At this 

 time the muscles have become acid and have ceased altogether to be 

 irritable. When the temperature has been raised beyond 70 no further 

 yield of free gases is obtained. 



If the muscle is treated with phosphoric acid at 0C., and sub- 

 sequently heated to assist the liberation of gas, a sharp evolution 

 occurs, of short duration and yielding but a small amount. If 

 the acid be added to a preparation subjected to a temperature of 

 20 50 C., at a time when the discharge has ceased to be volu- 

 minous, a brief acceleration of the discharge will result, followed by 

 complete and final stoppage. 



secondary, If the muscle is kept in the apparatus beyond 



or putrefac- the time at which the first discharge subsides, the 



tive, dis- liberation of gases begins again, even without the 



addition of an acid. This constitutes a secondary 



discharge, and is due to putrefaction; it may begin 



G. 23 



