(1. Try tin- effect . .f adding to the pure m/8 XaCl or m S XaBr 

 a little m S KC1 solution: e. g., <) vols. m S XaCl -)- I vol. m/8 

 KC1. How d.>cs the KC1 influence the behavior of the muscle? 



MO. Muscular t:^itcliiii</ in salt solutions. Sensiti.::int/ and de- 

 sensiti.'iiii/ actiini of 'I'driotts salt solutions, d ret pine record. The 

 muscle (gastrocnemius) is attached to the extremity of a bent glass 

 rod by a wire encircling' bone and rod. and is arranged to pull 

 vertically downward on the short arm of the light muscle lever. 

 Connection is made with the lever by a silk thread attached to 

 an S-shaped honk passing through the tendon. The glass rod 

 with the attached muscle is immersed in the solution contained in a 

 beaker, which stands on a block s< > that the solution can be readily 

 withdrawn without disturbing the muscle (see demonstration). 

 Test the action of the following solutions. The muscle is arranged 

 for the lever to write on a slowly moving drum. Take a base line 

 with the muscle in Ringer's solution. 



a. Transfer the muscle from Ringer's solution to a mixture of 

 7 vols. m/8 XaCl -{- i vol. m/8 KC1 by substituting a beaker with 

 j;o cc. of this solution for that containing the Ringer. Make the 

 change quickly, but be careful to avoid jarring. Xote the behavior 

 of the muscle and the characteristics of the contraction-curve in 

 this solution, tone-change, etc. At the end of _' minutes return 

 tn Ringer. Xote the effect. 



b. After the muscle has been in Ringer 2 or ^ minutes transfer 

 to pure m S Xal'.r; leave in this solution exactly 4 minutes. Then, 

 while the drum is moving transfer to the XaCl-KCl mixture. 

 Xote the difference in the resulting activity. After _' minutes return 

 to Ringer as before. Result? 



Repeat this experiment using Xa.,S< ), instead of m 8 Xal'.r. 

 Xote the difference in action. Xote carefully the behavior ot the 

 muscle both /;/ the solution and at the moment ot exposure to the 

 air when the transfer is made. (Contact-Irritability, shown espe- 

 cially after treatment with solutions () f salts whose anions precipi- 

 tate calcium; as XaK. X a, .('._,< >,. etc.) Xote also carefully the be- 

 havior in the XaCl-KCl solution. Leave here _' minutes and then 

 transfer to Ringer. 



e. l)cscnsiti:::in</ salts. Repeat using m S CaCI, instead of 

 m S Xal'.r. Xote the difference in effect. U this action of Cat | 

 reversible? If there is time try also m S MgCl... 



2OO. Influence of muscle poisons Yeratrin. Inject one or (wo 

 drops of a saturated solution of vcratrin into the dorsal Ivmph sac 



