Compounds of Pharmacological 

 Interest in Coelenterates 



John H. Welsh 



Biological Laboratories, Harvard University, Cambridge, Massachusetts 



The nematocysts of coelenterates appear to serve two principal 

 functions: one, a means of protection, the other, a role in feeding. 

 A person once badly stung by Physalia, Cijanca or certain of the 

 cubomedusae avoids contact with one of these a second time. It 

 may be assumed that an animal that is stung and survives also may 

 avoid future contact with a coelenterate if it is capable of learning. 

 More important, perhaps, to the coelenterates, is the paralyzing or 

 relaxing action of the contents of the nematocysts when injected 

 into their prey. 



Since the very early years of this century, efforts have been 

 made to identify the substances in coelenterates that are responsible 

 for the symptoms that result from their sting. In most of the earlier 

 work, extracts of whole coelenterates or of nematocyst-bearing 

 parts (tentacles and acontia) have been used. Therefore, it has not 

 been possible to attribute an observed action to nematocyst con- 

 tents. The recently developed methods of isolating clean nemato- 

 cysts will obviate this difficulty if it can be shown that they lose 

 none of their contents during the isolation procedure. 



A condensed and incomplete summary of substances or frac- 

 tions obtained from various coelenterates follows. Some of these 

 derive from nematocysts; others, almost certainly, do not. 



I. Early attempts to isolate toxic components of coelenterates by 

 Richet and Portier (19, 20, 21) yielded three active extracts: 

 "thallasin," "congestin" and hypnotoxin." None of these was chem- 

 ically identified and each was doubtless a mixture of substances 



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