168 EXPERIMENTAL PHARMACOLOGY 



EXPERIMENT XVII. 



Chloral Hydrate, Urethane, Paraldehyde, Chloretone. 

 (Frogs: Central Nervous System.) 



1. Into the anterior lymph sac (Fig. 66) of a frog in- 

 ject (see Figs. 125 and 126) one cubic centimeter of four 

 per cent chloral hydrate solution. Place the frog on 

 moist cotton in a battery jar and observe its symptoms. 

 Try its reflexes from time to time by touching it. Turn 

 it over and see if it can regain its normal position. Are 

 there any symptoms of stimulation? Some local irritation 

 may be caused by the drug when first injected. How long 

 does it take for the animal to become completely narco- 

 tized? How do the symptoms compare with those pro- 

 duced by ether, chloroform or nitrous oxide! 



2. Into the anterior lymph sac of another frog inject one 

 cubic centimeter of a ten per cent urethane solution. Care- 

 fully observe its symptoms, noting the condition of the 

 reflexes, power of equilibrium, etc., from time to time. 

 How does this drug compare with chloral or ether? 



3. Inject another frog with one-half cubic centimeter of 

 paraldehyde. Observe its actions carefully and compare 

 these with those manifested by the other frogs. What 

 structures or organs are chiefly concerned in the produc- 

 tion of the symptoms you observe! How would a decere-. 

 brated frog act under paraldehyde? 



4. Inject a fourth frog with chloretone solution. This 

 solution can be made up as f ollows : Place about half a 

 gram of chloretone crystals in a beaker and pour a few 

 drops of absolute alcohol over the drug. The chloretone 

 should soon dissolve. Now add water until faint traces of 

 a precipitate (white) begin to appear. Then add just 

 enouf/li alcohol to redissolve the precipitate. Of this solu- 

 tion one or two cubic centimeters may be injected into the 

 frog. (Chloretone is also sometimes dissolved in olive oil 

 for administration to animals.) 



