76 THE BIOLOGY OF HYDRA : 1961 



immersion objective we brought the tip of a conventional capillary 

 microelectrode close to the cell body of one of the bipolar cells 

 miderlying the epidermis between the tentackilar bases. Occasional- 

 ly we picked up fairly strong, slow spikes, lasting 20 to 50 millisec- 

 onds and somewhat various in shape. They were always 

 associated with strong tentackilar contractions and always clearly 

 came before any movement was discernable in the area under ob- 

 servation. The tentacular reaction to glutathione did not elicit action 

 potentials, however. 



The other successful preparation also gave action potentials 

 associated with strong muscle contractions. Here we used an intact 

 hydra suspended from the surface film and surrounded by a 

 wire ring to immobilize the animal and to be the indifferent elec- 

 trode. The microelectrode picked up action potentials after pene- 

 trating the basal disk, when the gastrodermal longitudinal muscles 

 contracted. 



We believe that these electrical changes associated with either 

 tentacular or column "quick withdrawal" responses were nerve 

 action potentials, not muscle action potentials, since they came 

 well prior to muscle contraction, only with the quick, coordinated 

 contractions of all the muscle fibers, and since we only picked them 

 up sporadically. 



HESS: From a nerve cell? Can you get your electrode inside a 

 nerve cell of hydra? 



PASSANO: We think that they are from nerve cells, since we 

 attempted to place our recording electrode in the small bipolar 

 cells that underlie the epidermis. Since we did not have direct 

 coupled amplifiers available, we are not able to say whether or 

 not we ever penetrated nerve cells. Frankly, I doubt it. 



