166 EXPERIMENTAL PHARMACOLOGY 



Now stimulate one vagus nerve and record the result. 

 When all the pointers return to normal inject a fair sized 

 dose of alcohol. Does this affect the blood-pressure? How 

 does the spleen or kidney tracing obtained now compare 

 with the one produced by adrenaline ? How do you explain 

 this? What mechanical factors are involved? Inject an- 

 other dose of adrenaline and see if you can determine two 

 phases to the adrenaline action. How do you explain this? 

 Now obtain tracings showing the action of brandy, ure- 

 thane (ten per cent solution, two cubic centimeters for the 

 first injection), and chloral (four per cent solution, one 

 cubic centimeter for the first injection). The oncometer 

 tracing is liable to become unsatisfactory after three or 

 four records have been obtained from it. Can you deter- 

 mine what this is due to! (See Fig. 160.) How do ure- 

 thane and chloral affect the blood-pressure and respira- 

 tion? Which is the more active drug? Kill the animal 

 by closing off the respiration. Do you get an oncometer 

 tracing? How is the blood-pressure affected? 



5. If time permits, carry out the following dissections : 

 Open the chest by a median longitudinal incision and pull 

 the heart (pericardium) over to the right side. Deep down 

 in the chest (behind the diaphragm as it arches upward) 

 and a little way latterly from the median line you will find 

 the esophagus and the aorta. These can be traced down 

 from the upper part of the chest and from the heart. Look 

 for the vagus trunks on the esophagus (Fig. 161). Be- 

 neath the pleura at the side of the spinal column you can 

 find the main branches of the thoracic sympathetic. Pick 

 these up and trace them down behind the diaphragm. 

 Open the abdomen, divide the diaphragm, and pull the 

 stomach and liver to the right. Can you trace the passage 

 of these sympathetic fibers from the chest down into the 

 abdomen? Observe carefully the exact position which the 

 fibers occupy and see into what kind of a structure thev 

 pass. If the stomach, liver and diaphragm were in their 



