DISCUSSION ON NERVOUS SYSTEM 75 



SLAUTTERBACK: Before the argument is lost Iw default Td 

 like to inject a little bit of skepticism. I have no way of proving that 

 the nervous system does not exist, in fact, I am not sure that I 

 really doubt it. ( I was expecting Dr. Fawcett to stand up ahead of 

 me and say this.) But I would like to say that most of us who have 

 hunted for nerve cells with the electron microscope have been un- 

 able to find any. It is at least possible that this is because the 

 morphology of invertebrate nerves or hydra nerves is not readily 

 recognizable. But tliis is disturbing in view of the fact that there 

 are clear morphological criteria for the identification of nerves in 

 vertebrate tissues; they are readily recognizable with the elec- 

 tron microscope. In fact, I'd say more easily identified than in the 

 light microscope. Then too, it seems to me that the musculo-epitheli- 

 al cells are so beautifully organized for conduction in hydra, that 

 we don't really have to postulate the existence of a nervous system 

 which we can't see in order to account for the behavior pattern. I 

 recognize that it will probably take arguments more cogent than 

 these to refute a concept which has delighted liiologists for at 

 least 70 years. I have only to say that we can't see a nervous 

 system. We'd like things a little more sure. 



HESS: Muscle to muscle connections, of course, are present e\'en 

 in mammalian smooth muscle. It wouldn't be an impossible situa- 

 tion for hydra to use muscle to muscle transmission to execute its 

 movements. 



PASSANO: I doubt that this answers our discussion, l)ut it 

 might be of interest to tell this group of our success in recording 

 action potentials from hydra. A few years ago C. B. McCullough 

 and I tried to find out whether or not hydra showed non-decre- 

 mental through conduction by looking for ner\e action potentials. 

 We attempted to pick up actix ity of indixidual neurons, but what 

 we got, probably, were near-simultaneous action potentials from 

 several contiguous cells. 



We had results with two types of preparations. The tentacle- 

 hypostome preparation (we cut off and discarded the column just 

 below the tentacular base) was threaded on a silver rod through 

 the mouth. In addition to serving to immobilize the animal the 

 rod served as a neutral electrode. While observing with a water 



