MECHANISM OF SECRETION 89 



3. Inject a small amount of pilocarpine nitrate (2 or 3 milligrams) into the 

 saphenous vein. This produces an intense secretion. 



4. Inject a small amount of atropine sulphate (5 milligrams) into the vein. 

 The flow produced by pilocarpine immediately stops. 



6. Stimulate the chorda. The strongest stimulation produces no effect. 

 Atropine has paralysed the nerve endings. 



6. Stimulate the sympathetic. A few drops of saliva may be secreted. 

 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 duodeum 

 and bring it up 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 duodeum. 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 clipped mucous 

 membrane with - 5 per cent, hydrochloric acid, cooling the decoction, neutralising 

 with dilute alkali, and filtering. It contains secretin, which has the effect of 

 producing a rapid flow of pancreatic juice when injected into the circulation. 



2. Inject pilocarpine nitrate and compare the effect with that of secretin. 

 The mamma. A lactating animal (cat) is anaesthetised and a cannula tied into 



the external jugular vein. Vaseline the fur over one of the mammas, and arrange 

 the animal so that this gland slightly overhangs the edge of the animal board. 

 Cut away the nipple of that mamma and make a short transverse incision into 

 the substance of the gland. Still any bleeding with cotton-wool or with dilute 

 suprarenal extract. Some milk may ooze out : it will run down the vaselined 

 fur, and can be caught in a beaker. 



1. Inject into the vein 1 c.c. of a 10 per cent, decoction of corpus luteum 

 (filtered). Milk will, in a minute or two, exude and drop rapidly from the gland. 



2. Inject into the vein 1 c.c. of a 10 per cent, decoction of posterior lobe of 

 pituitary body. The same result will ensue, but the flow will be more rapid. 



The kidney. In an ansesthetised rabbit or cat tie a cannula into the jugular 

 vein and connect the carotid with a manometer for taking blood-pressure. 

 Make an incision through the skin and muscles on the left side of the abdomen 

 near the back over the situation of the kidney, which is easily felt. After ex- 

 posing the kidney, bring it towards the surface, clear it partly of fat, and allow 

 it to lie in a suitable plethysmograph (fig. 68) the margins of which have been 

 vaselined, and place over it a glass cover also well vaselined : the cover is clipped 

 down on to the plethysmograph. The blood-vessels and ureter pass out at a 

 chink (g) left on one side of the plethysmograph ; the chink is made airtight 

 with vaseline. A tube leads from the plethysmograph to a piston recorder (p.r.) 

 writing on smoked paper. Make another incision in the lower part of the 

 abdomen in the middle line ; find the urinary bladder ; hold it up with two pairs 

 of clamp forceps ; loop a ligature round it just outside these ; make an incision 

 into it, and introduce a glass cannula, which must then be tied in. The urine 

 can be led from this cannula over the side of the animal by a rubber tube, and 

 the drops can be registered by a drop-recorder. 



1. Inject pituitary extract into the vein, and record the effect on blood- 

 pressure, kidney, volume, and urine. 



2. Inject a few milligrams of caffeine citrate into the vein, and record its 

 effect in the same way. 



3. Inject atropine sulphate (5 milligrams). This has no effect on the secretion 

 of the kidney (compare with its effect on salivary secretion). 



