258 ON THE PRESERVATION OF TENDER MARINE ANIMALS. 



Silver is reduced principally in the intercellular substance, and 

 therefore used to demonstrate the cell margins. Chloride of 

 Palladium is used for the same purposes as Gold. 



Besides preserving the animals in a natural state, it is also 

 necessary to preserve them in an expanded state, and as all animals 

 naturally roll themselves up and retract their soft appendages 

 when placed in a poisonous solution, it is attended with great 

 difficulty to kill them so rapidly that they have not time to 

 retract. 



Sometimes it is possible to kill Hydroids and the Zooids of 

 Corals with Osmic Acid so rapidly that they do not contract. 

 Much more difficult this is with the Actinije (Sea anemones). 

 The best way to preserve these latter in an expanded state, is to 

 warm them to a temperature of about 43" C. Hereby they do 

 not contract, and are lamed partially by the high temperature. 



They can then be chloroformed, the only poison which has any 

 effect on them (1), and treated with Osmic Acid, or any of the 

 other re-agents. 



The Osmic Acid is a high Oxide 3 5 of the Metal Osmium 

 belonging to the Platina group with a specific weight of 22. It 

 is exceedingly rare, and derived only from the remains of material 

 out of which Platina has been obtained. 



F. E. Schulze was the first to introduce this substance into the 

 Zoological Laboratories. And more discoveries are due to the 

 application of this re-agent, than to any other. 



(1) The brothers Hertwig have shown that Curare and Cyanite of 

 Potassium, and also Morphine do not affect them. A bit of Cyanite of 

 Potassium half as big as a sea anemone placed in its stomach, does not 

 kill it. 



