ARECOLINE, ADRENALINE, ATROPINE, ETC. 297 



too small this is seldom the case then a second may be 

 given but this reduces the vitality of the animal markedly 

 and is best avoided.) 



Get the animal into as good condition as possible and 

 (take a normal) inject one cubic centimeter (less if tin* 

 animal is small) of arecoline solution. The response will 

 probably be profound. Wait for the heart to beat slowly 

 again. When the bronchioles are greatly constricted in- 

 ject one cubic centimeter of adrenaline. \> f 'aii lor the drug- 

 to be carried around. The result should be striking. How 

 do you explain this ? (If the first dose of arecoline was too 

 small this is seldom the case then a second may be given 

 but this is best avoided.) 



Empty out the pilocarpine (be sure the bull-dog on the 

 rein does not leak) and fill the burette with atropine solu- 

 tion (one cubic centimeter equals one milligram). 



Take a normal record and inject one cubic centimeter 

 (or one and one-fourth cubic centimeters) of arecoline. 

 When the action is marked inject one cubic centimeter of 

 atropine. Wait for the drug to circulate. What do you 

 observe? Explain all mechanical factors. Inject one-half 

 cubic centimeter of arecoline. What conclusions can you 

 draw? 



Empty out the areeoline and fill the burette with one- 

 half per cent barium chloride solution. Barium acts pre- 

 sumably directly on the smooth muscle fibers. Remember 

 the animal has Itad atropine. Take a normal record (the 

 animal will probably be greatly weakened by this time) 

 and inject five cubic centimeters of barium solution (three 

 cubic centimeters if the animal is small). What do you 

 observe? It will take some time for the action to become 

 marked. Is the heart irregular? Barium acts somewhat 

 like digitalis and in some respects resembles adrenaline. 

 Do the bronchioles contract? If so inject two cubic centi- 

 meters of adrenaline. Do they respond to this? Kill the 

 animal with a bie; dose of barium. How does barium act on 



