58 LABORATORY MANUAL OF GENERAL PHYSIOLOGY 



column. Stimulate the right sciatic near the column with a submaximal 

 stimulus. Do the muscles contract? Try the left sciatic. Remove skin 

 over right gastrocnemius and apply electrodes directly to muscle. 

 Explain. Discuss the theories of curarization of Bernard, Lapicque and 

 Bancroft. Cf. Starling, "Physiology," 7th Ed., 1936, p. 126. Text 

 p. 359. 



29. Salt Effects on Muscle. — Carefully remove curarized small muscles 

 (sartorius, biceps, tibials, etc.) from the leg of a frog. Place in the 

 following solutions. Change each solution 2 or 3 times to remove 

 foreign matter. 



(a) M/4 sugar solution 



(b) 4 vols, m/4 sugar + 1 vol. m/8 NaCl 



(c) M/8 NaCl. When irritability is lost add drops of CaCl2 



(d) M/8 NaBr. When irritability is lost add drops of CaCl2 



(e) 24 vols, m/8 NaCl + 1 vol. m/8 CaCl2 

 Cf) M/8KC1 



Cg) M/12 CaCl2 (why not m/8?) 



(h) M/8 sea water (sea water equivalent to 0.52m NaCl) 



(i) Controls in Ringer's solution, including one in ice box for several 

 days. 



Note any immediate effects. Test irritability with single induction 

 shocks at 10 min. intervals. Note any contraction, permanent shorten- 

 ing, twitching. Which solutions preserve irritability longest? After 

 irritability is lost, test recovery in Ringer solution (cf. Hober, "Physika- 

 liche Chemie der Zelle und der Gewebe," 6 Auf., p. 641). The twitching 

 in sodium salts was first observed by Biedermann (cf. Chao, Am. J. 

 Physiol., 109: 550, 1934). Text p. 291. 



30, Effect of Veratrin. — Inject 0.5 cc. of veratrin solution into the 

 dorsal lymph sac of a frog with brain pithed. Note any effects on reflexes 

 and on general activity. Make a gastrocnemius sciatic preparation and 

 record a twitch (break shock). Note double peak and prolonged relaxa- 

 tion. Stimulate several times. Does the effect wear off? Test the effect 

 of rest (cf. Howell, 12th Ed,, p. 33; Bayliss, p. 734). Text p. 359. 



X. ELEMENTARY PHYSIOLOGY OF THE CENTRAL NERVOUS 



SYSTEM 



1. Action of Strychnine. — Pith the brain (not cord) of a frog and inject 

 a few drops of 0.5% strychnine sulphate in the dorsal lymph sac. Sus- 

 pend the frog by a bent wire hook through the jaw. After a few minutes 

 apply a weak tactile stimulus to any part of the body. When contraction 

 ceases, touch at other points. Describe result. What effect has the drug 

 on graded resistances in the C.N.S.? Text p. 359. 



2. Delayed Conduction at Synapse. — Make a gastrocnemius prepara- 

 tion retaining both sciatic nerves including the connecting bit of vertebral 



