232 THE BIOLOGY OF HYDRA : 1961 



BURNETT: We once found that dilute concentrations of bovine 

 testes hyaluronidase stimulated the feeding response. At that time 

 we assumed that our enzyme preparation was contaminated with 

 glutathione. A more recent preparation consisting of crystals quite 

 different from our original preparation was not effective. 



LENHOFF: These are factors that you have to consider. First 

 you must dialyze to remove endogenous glutathione. For example 

 we found some of our enzyme preparations elicted a response before 

 dialysis but not afterwards. 



KLINE: Some compounds may cause the mouth to open without 

 producing the true feeding reflex. 



LENHOFF: Definitely. You can get mouth opening, but not the 

 true feeding reflex from many compounds, usually toxic ones. As 

 Dr. Loomis pointed out in his original paper, the best proof that a 

 compound can initiate the feeding reflex is to give the Hydra some 

 inert material impregnated with the compound you are testing. If 

 the Hydra ingests the inert material, then a true feeding reflex was 

 elicited by that compound. 



