264 



EXPERIMENTAL PHARMACOLOGY 



(see Fig. 234). What do you observe ? What are your con- 

 clusions 1 Consult your text-book on physiology for further 

 explanation regarding the innervation of the lungs. Now 



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Fig. 235. Lung and heart tracings from a turtle showing the effect of electrical 

 stimulation of the right vagus nerve (first contraction and inhibition) and of mechanical 

 stimulation (tearing) of the same nerve (second and third records). 



make a careful dissection of the nerves (and sympathetic 

 branches) on the opposite side of the neck. Make a sketch 

 of these nerves for future reference. 



It is exceedingly desirable in making the preliminary dis- 

 section to remove as much as possible of the skeletal mus- 

 culature. This prevents movements which may be confused 

 with the lung contractions. 



