56 



EXPERIMENTAL PHARMACOLOGY 



right optic lobe and remove it. Be careful to avoid injuring 

 the thalamencephalon or cerebellum. Do not use too much 

 chloroform. It will produce a profound anesthesia and the 

 animal may not survive. Tie a thread (not tightly) around 

 the right fore leg and place the frog on moist cotton in a 

 covered battery jar to recover. A few hours later (or next 



Position of 



foramen 



mdqnum 



AHatpin,or sharp 

 ' Pinted probe 



Fig. 49. Method of pithing a frog. A towel is sometimes wrapped around the animal 



to facilitate holding it. 



day) carefully observe the actions of the animal and com- 

 pare these with those of the frog with the cerebrum re- 

 moved. How do these symptoms differ from those exhib- 

 ited by a frog which is just being anesthetized? Theoret- 

 ically what symptoms should be shown by a frog which was 

 injected with a drug that would depress the cerebrum alone :' 

 Or the optic lobes alone? Place both frogs in the water and 

 observe their movements. It will be instructive if another 

 frog can be operated on and the left optic lobe removed. 



