EFFECT OF ANESTHETICS UPON LIVING PROTOPLASM. 313 



in which the eggs are contained is allowed to freeze, the egg 

 cytoplasm becomes coagulated. Such eggs are permanently in- 

 jured by the treatment. In one experiment eggs were exposed 

 to a temperature of - -6 C. for 10 minutes. In spite of the fact 

 that no ice was observed in the tube containing the eggs, the pro- 

 toplasm when tested was found to be coagulated. Thus in the 

 case of cold also there is apparently a turning point, at which the 

 viscosity of the cytoplasm no longer decreases but suddenly 

 shows a marked increase. 



When sea-water is diluted, the resultant hypotonic solution is 

 one of the best (i.e., least injurious) anesthetics. A solution 

 made up of equal parts of sea-water and distilled water is an 

 excellent anesthetic. There is nothing unusual about this, for 

 is has long been known that water anesthetizes nerves. This 

 knowledge dates back as far as I869, 1 and water has occasionally 

 been used in various surgical operations. In the sea-urchin egg 

 those dilutions of sea-water which prevent cell division are the 

 very ones which produce a marked decrease in cytoplasmic vis- 

 cosity. On the other hand, too great a dilution causes coagula- 

 tion ; this effect is produced when the eggs are dropped into dis- 

 tilled water. 2 



Not all anesthetics cause a decrease in cytoplasmic viscosity. 

 Some produce quite the opposite effect. 



Many students of anesthesia confine their attention to fat 

 solvent anesthetics. This in spite of the fact that magnesium 

 sulphate in concentrated solution is apparently the best anes- 

 thetic for most marine invertebrates. As far as I can discover 

 magnesium sulphate was first used by Tullberg. 3 Its effect ap- 

 pears to be largely an osmotic one, for the salt acts best in hyper- 

 tonic solution. This is also indicated by the observations of Loeb 4 

 on hydroids. Loeb found that the regeneration of hydroids could 



1 Braun, H., Local Anesthesia, English translation by Shields, Philadelphia. 

 1914, p. 62. 



2 Heilbrunn, L. V., BIOL. BULL., 1915, XXIX., 149. 



3 Tullberg, T., Verhandl. d. biolog. Vereins Stockholm, 1891, IV., Nr. 1-2, 

 p. 4, cited after Gerould, J. H., Bull. Muss. Coinp. Zodl., Harvard, 1896, XXIX.. 

 121. 



3 Loeb, J., Untersuchungen zur physiologischen Morphologie der Thiere, 

 Wurzburg, 1891-1892. 



