PRACTICAL EXERCISES 



457 



easily laid on electrodes by means of the ligature on the lingual. On 

 stimulating the chorda, the flow of saliva through the cannula will be 

 increased. The current need not be very strong. If the flow stops 

 after a short time, it can be again caused by renewed stimulation after 

 a brief rest. A quantity of saliva may thus be collected, and the experi- 

 ments already made with human saliva repeated. 



(2) Expose the vago-sympathetic nerva in the neck on the same 

 side ; ligature it ; divide below the ligature ; and note the effect pro- 

 duced by stimulation of the upper end on the flow of saliva. 



(3) Set up another induction-machine, and connect it with electrodes. 

 Stimulate the chorda, and note the rate of flow of the saliva. Then, 

 while the chorda is still being excited, stimulate the vago-sympathetic, 

 and observe the effect. If the experiment is successful, finish by 

 stimulating the chorda for a long time. Then harden both sub- 



Digastric 



Muscle (cut). 



Hypoglossal 

 Nerve. 



Mylo-hyoid Lingual Wharton's 

 Muscle (cut). Nerve. Duct. 



Fig. 174. Dissection for Stimulation of Chorda Tympani (after Bernard). 



maxillary glands in absolute alcohol, make sections, stain with carmine, 

 and compare them. 



7. Effect of Drugs on the Secretion of Saliva. (i) Proceed as in 

 6 (i), but, in addition, insert a cannula into the femoral vein (p. 218). 

 On the cannula put a short piece of rubber tubing, filled with 0-9 per 

 cent, salt solution and closed by a small clamp, or a small piece of 

 glass rod, or a pair of bulldog forceps. While the chorda is being 

 stimulated inject into the vein 10 to 15 milligrammes of sulphate of 

 atropine by pushing the needle of a hypodermic syringe through 'the 

 rubber tube. This will stop the flow of saliva, and abolish the effect 

 of stimulation of the chorda. See whether the sympathetic is also 

 inactive, and report the result. 



(2) Now empty the cannula in the submaxillary duct by means of a 

 feather, and fill it with a 2 per cent, solution of pilocarpine nitrate by 

 means of a fine pipette. Fill also the short rubber tube attached to 

 the cannula, and close it again. Compress the tube, and so force into 



