ON THE USE OF MAGNESIUM IN STUPEFYING 

 MARINE ANIMALS. 



ALFRED G. MAYER. 



It is well known that Tullberg, 1892, discovered that an excess 

 of magnesium added to sea-water causes anesthesia in marine 

 animals, thus permitting them to be killed in an expanded state. 



During the course of some physiological experiments carried 

 out at the Marine Laboratory of the Carnegie Institution of Wash- 

 ington at Tortugas, Florida, I found that marine animals can be 

 anesthetized much more rapidly and completely than by Tull- 

 berg's method if we simply place them in a pure aqueous solution 

 of MgSO 4 or MgCl, of three eighths molecular concentration. 

 They then subside into complete relaxation without initial stimu- 

 lation, and after remaining for an hour or two in the solution they 

 may be killed in any manner whatsoever without becoming dis- 

 torted through contraction. Some distortion is often produced 

 in Tullberg's process, due to the calcium and sodium of the sea- 

 water, but in a pure aqueous solution of magnesium the relaxa- 

 tion of the muscles is complete. This method has been tried 

 upon scyphomedusas, ctenophorae, actinians, annelids, nemertians, 

 phascolosoma, and nudibranchs with marked success, and appears 

 to be especially suitable for the stupefying of highly sensitive and 

 contractile marine animals which become hopelessly distorted if 

 killed by ordinary methods. 



It is interesting to observe however that while magnesium is 

 the most potent anesthetic for the neuro-muscular system it is 

 the most powerful stimulant among the ions of sea-water or of 

 blood-salts for the movement of cilia. Indeed I find that the ions 

 of Na, Mg, K and Ca affect cilia in a manner the exact opposite of 

 their effect upon muscles and nerves. Thus Na is the most power- 

 ful neuro-muscular stimulant, and the most pronounced inhibitor 

 for the movement of cilia. Mg is the greatest inhibitor for nerves 

 and muscles and the strongest stimulant for the movement of cilia. 

 A weak concentration of K at first excites and then depresses the 



34i 



