GENERAL PHYSIOLOGY OF MUSCLE AND NERVE TISSUE 57 



may apply heat to the fresh nerve so gradually that the nerve may 

 be actually cooked without causing a contraction of the muscle 

 which it supplies. 



The problem which we have next to solve is to apply an electric 

 stimulus gradually. 



1. Appliances. Fleischl's rheonom; one Daniell cell; myograph; 

 contact key; galvanoscope; saturated solution of zinc sulphate; five 

 wires; frog; operating case. 



The rheonom is constructed as in Fig. 34. Its essential features 

 are: g, the non-conducting base with circular groove; P, the non- 

 conducting rotatable, central standard; the battery binding posts, 

 having zinc connection with the groove; the rotating binding posts, 

 having zinc limbs dipping into the groove. 



2. Experiments and Observations. Set up an apparatus as 

 shown in Fig. 34, after amalgamating the zinc tips which dif> into 

 zinc sulphate. Fill the groove with zinc sulphate. 



FIG. 34 



(1) Find and mark the zero position for the rotating limbs of 

 the rheonom i. e., find the position which will give no deviation 

 of the detector needle when the contact key is closed. 



(2) Find and mark the position which the rotating limbs occupy 

 when the detector needle indicates 10. 



(3) Find and mark in succession each higher increment of 10, 

 until the maximum is reached. 



(4) Rotate the limbs so gradually as to cause the detector needle 

 to rotate with slow and regular motion from the zero position to 

 the maximum position and back. 



(5) Make a gastrocnemius muscle-nerve preparation, mount it 

 in the myograph; change the wires from the galvanoscope to the 

 electrodes of the myograph; place the limbs of the rheonom in the 

 maximum position; close the key. With the closing of the key 

 the maximum current is instantly thrown into the nerve and serves 

 as a strong stimulus, in response to which the muscle contracts. 



(6) Place the limbs of the rheonom in the minimum position; 

 close the key. Inasmuch as the muscle-nerve preparation is much 

 more sensitive to electricity than is the low-resistance galvanoscopy, 

 the muscle will probably respond when the conditions are as above 

 indicated. Theoretically, a zero point exists. Practically it may 



