IO4 EXPERIMENTAL PHYSIOLOGY 



pass a " finder " into the aperture. Substitute for the "finder" a very 

 fine metal or glass cannula, and tie this in : a piece of small rubber 

 tubing can be used to conduct the secretion beyond the edge of the 

 jaw, where it can be allowed to drop into a beaker. 



On the same side of the neck make a longitudinal incision through 

 the skin and fascia, and separate the muscles so as to expose the 

 carotid artery and the common trunk of the vagus and sympathetic 

 nerves. Ligature this combined nerve low down, and place the upper 

 end on a second pair of electrodes. The two pairs of electrodes for 

 chorda and sympathetic respectively are connected to a commutator 

 without cross-wires, and this with the secondary coil, so that stimula- 

 tion can be led into either pair at will. 



1. Stimulate the sympathetic. A few drops of thick viscid saliva 

 are secreted. (In the cat, stimulation of the sympathetic yields an 

 abundant secretion.) 



2. Stimulate the chorda. There is a rapid flow of watery saliva, 

 lasting as long as the excitation is continued. 



3. Inject a small amount of pilocarpine nitrate (2 or 3 milligrammes) 

 into the saphenous vein. This produces an intense secretion. 



4. Inject a small amount of atropine sulphate (5 milligrammes) into 

 the vein. The flow produced by pilocarpine immediately stops. 



5. Stimulate the chorda. The strongest stimulation produces no 

 effect. Atropine has paralysed the nerve endings. 



6. Stimulate the sympathetic. Saliva will be secreted as before. 

 The dose of atropine is insufficient to abolish the action produced 

 through the sympathetic. 



The pancreas. A dog is anaesthetised and a cannula tied into the 

 saphenous vein. Open the abdomen by an incision in the linea alba. 

 Find the duodenum and bring it to the surface : the pancreas is seen 

 in the mesentery within its curve. The duct of the gland canal 

 of Wirsung may be found without difficulty near the lower end of 

 the part of the gland which is in contact with the duodenum. Isolate 

 a short length of the duct with forceps ; pass a wet ligature round it 

 and slip a pointed piece of paraffined paper under it. Make a snip 

 into the duct with fine scissors, introduce a finder, substitute for 

 the finder a fine metal or glass cannula, and tie this in. Attach 

 a short piece of rubber tubing to the cannula, bring the end of 

 this outside the wound, and let the drops of secretion fall into a 

 beaker. 



1. Inject into the saphenous vein 5 c.c of an extract of duodenal 

 mucous membrane of any animal. The extract is made by boiling the 

 chopped mucous membrane with 0*5 per cent, hydrochloric acid, cooling 

 the decoction, neutralising with dilute alkali, and filtering. It con- 



