and Laboratory Methods. -1-5 



The Technique of Biological Projection and Anesthesia of 



Animals. 



COPVKIGHTED. 



X. THE ANESTHESIA OF ANIMALS— Continued. 



CcELENTERATA : Hydra. — Hydras move so slowly that there is little need 

 for anesthesia in studying them alive, but chloretone may be used with fair suc- 

 cess in connection with a killing agent in preparing expanded specimens, and 

 with entire success in dissociating the cells while the cells themselves are alive. 



To kill hydras expanded, place the animals in a watch-glass with fifty drops 

 of water, or enough to afford them room for full expansion. Allow them to 

 stand quietly until fully expanded. Add one per cent, solution of chloretone 

 carefully one drop at a time at intervals of a few minutes, or as often as the ani- 

 mals are seen to have expanded after the contraction caused by the addition of 

 the drug. When the proportion of chloretone solution equals one-fifth to one- 

 seventh the volume of water in the watch-glass and the hydras do not contract 

 quickly when touched with a needle, add rapidly about two volumes of five per 

 cent, formalin solution or other killing agent, and mount them in hollow-ground 

 slides, or in the usual manner. 



To demonstrate the dissociated cells of the hydra, treat as above for killing, 

 but do not add formalin until dissociation is observed to have reached the 

 desired degree and the amoeboid motion of the cells has been studied. The 

 gradual separation of the cells may be observed with a quarter or half-inch 

 objective, either in the watch-glass or after transferring the hydra and a few drops 

 of the solution to a slide by means of a pipette. Nematocysts are easily demon- 

 strated, some with threads coiled and others extended. Amoeboid motion may 

 also be observed in cells discharged from the hydra's mouth in a brownish col- 

 ored granular mass when the hydra contracts to its minimum size under the 

 influence of a strong dose of chloretone solution. 



Vermes : Planarians. — These worms are interesting objects for the study 

 of ciliary action and the anatomy of the worm. Place a planarian in a watch- 

 glass, or on a hollow-ground slide in six drops of water and add two drops of 

 one per cent, chloretone solution. Muscular activity ceases in two minutes, or 

 less, but ciliary action may be studied for hours, and is best seen on the sides 

 of the body near the anterior end. The pharynx is protruded in many speci- 

 mens. When the animals are kept under observation for an hour or more, it is 

 usually necessary to add a drop of chloretone solution occasionally to control 

 returning muscular activity. This is due to two characteristics of chloretone, first, 

 its volatility, and second, the fact that animals become accustomed to it and 

 require larger doses to produce a given effect. 



To kill planarians with pharynx protruded, place them in a watch-glass, draw 

 off the water, cover them with one per cent, chloretone solution, and quickly 

 transfer them to five per cent, formalin. 



Earthworms. — -These common animals are of unequaled value for study in 



