POISONS. 241 



my experiments lead to no very instructive con- 

 clusion, they are, I think, worth stating. 



I first tried dissolving chloride of sodium in fresh 

 water till the latter was of the same density as sea- 

 water. Sarsiie dropped into such a solution con- 

 tinued to live for a great number of Ik urs ; but 

 they were conspicuously enfeebled, keeping for the 

 most part at the bottom of the vessel, and having 

 the vigour of their swimming motions greatly im- 

 paired. The tentacles and manubrium w^ere strongly 

 retracted, as in the case of exposure to fresh water, 

 and the tissues also became slightly opalescent. 

 Thinking that perhaps a fairer test would be only 

 to add as much chloride of sodium to the fresh 

 water as occurs in sea- water, I did so ; but the re- 

 sults were much the same. On now adding sulphate 

 of magnesium, however, to the amount normally 

 ])resent in sea- water, the Sarsise became more active. 

 1 next tried the effects of chloride of sodium dis- 

 solved in fresh water to the point of saturation, or 

 nearly so. The Sarsi?e, of course, floated to the 

 surface, and they immediately began to show 

 vsymptoms of torpidity. The latter became rapidly 

 more and more pronounced, till spontaneity was 

 quite suspended. The animals, however, were not 

 dead, nor did they die for many hours, their irrita- 

 bility continuing unimpaired, although their spon- 

 taneity had so cinnpletely ceased. The tentacles and 

 manubrium were exceedingly relaxed, which is an 

 interesting fact, as being the converse of that which 

 occurs in water containing too small a proportion of 

 salt. Lastly, to give the density hypothesis a still 



