194 EXPERIMENTAL PHYSIOLOGY. 



(c.) Excise a heart so as to get a spontaneously beating 

 ventricle, lead off from the base and apex of the latter, 

 observe the so-called " negative variation " with each con- 

 traction. 



4. Capillary Electrometer. 



(a.) Lead off a muscle to the two binding screws of a 

 capillary electrometer. The fine thread of mercury must 

 be observed with a microscope. 



LESSON XL. 



GALVANI'S EXPERIMENTS SECONDARY 



CONTRACTION AND TETANUS- 

 PARADOXICAL CONTRACTION KUHNE'S 

 EXPERIMENT. 



1. Galvani's Experiments. 



(a.) Destroy the brain of a frog, divide the spine about the 

 middle of the dorsal region, cut away the upper part of the 

 body, and remove all the viscera. Remove the skin from the 

 hind legs, divide the iliac bones and urostyle, taking care to 

 avoid injuring the lumbar plexus, which will remain as the 

 only tissue connecting the lower end of the vertebral column 

 with the legs. Thrust an S-shaped 

 copper hook through the lower 

 end of the spine and spinal cord 

 (Fig. 84). 



(b.) Hang the frog by means of 

 the hook to an ordinary iron tripod. 

 Tilt the tripod so that the legs of 

 the frog come in contact with one 

 of the legs of the tripod ; vigorous 

 contractions occur whenever the 

 frog's legs touch the tripod. 



(c.) Allow the frog to hang per- 



Fig.84.-Galvani'sExperi. Particularly without touching the 

 merit, tripod, and take a U-shaped piece 



