236 



PRACTICAL PHYSIOLOGf. 



[XLV. 



(/.) Vary the position of the 

 electrodes and note the variation 

 in the deflection. If they be equi- 

 distant from the equator, there 

 is no deflection. The greatest 

 deflection takes place when one 

 electrode is over the equator and 

 the other over the centre of the 

 transverse section of a muscle 

 composed of parallel fibres. The 

 deflection, i.e., the electro-motive 

 force, diminishes as the electrodes 

 are moved from the equator or the 

 centre of the transverse section. 

 In certain positions no deflection 

 is obtained. 



5. Negative Variation of the 

 Muscle-Current. 



(a.) Use the same 

 muscle preparation, 

 or isolate the gas- 

 trocnemius with 

 the sciatic nerve 

 attached. Divide 

 'the muscle trans- 

 versely, and lay the 

 artificial transverse 

 section on one elec- 

 trode, and the longi- 

 tudinal surface on 



the 



FIG. i6o.-Brush 



Eiectrodes of serve the extent of 



V.Fleischl. 



(&.) Adjust an induction coil 

 for repeated shocks, placing it at 

 some distance from the galvano- 

 meter. 



(c.) Take the demarcation- 

 current, observing the deflection, 

 arid allow the spot of light to 

 take up its new position on 

 the scale. Tetanise the muscle 

 through its nerve, and observe 

 that the spot of light travels 



