RECORDING PULMONARY BLOOD-PRESSURE 371 



for recording pulmonary blood-pressure. In this present 

 experiment, however, arrange first to take a record of the 

 action of tyramine. Record the blood-pressure (carotid) 

 and the respiration (stethograph). 



Tyramine is sold in the form of hypodermic tablets (0.020 

 gram % gram each) by Burroughs, Wellcome & Co. Make 

 a solution containing five milligrams to one cubic centi- 

 meter. (It may be advisable to inject this with a hypo- 

 dermic syringe into the external jugular or femoral vein 

 to avoid using more drug than is necessary.) 



Adjust the writing points on the drum, take a normal 

 record and inject one cubic centimeter. You should get a 

 rise in pressure which persists for some time. Wait for the 

 effects of this to wear off and save your animal as it will 

 need all the vitality it has for the next part of the experi- 

 ment. On what structures does tyramine act? To what 

 other drug is it most similar in action! How does it differ 

 from ergotoxine? 



Remove the stethograph and insert a cannula (see Fig. 

 279) into the left pulmonary artery. The injecting burettes 

 (femoral veins) contain ergamine (ten cubic centimeters 

 equal one milligram, see Experiment CII) and adrenaline 

 (1:10,000). Be sure the artificial respiration is being car- 

 ried out satisfactorily and that the animal does not get too 

 much (nor too little) ether. 



Adjust the writing points, take a normal and inject one- 

 half cubic centimeter of adrenaline. Is your adrenaline 

 preparation satisfactory? (Many samples are spoiled be- 

 fore the bottles are opened and an exposed solution rapidly 

 deteriorates.) (See Fig. 311.) 



When the records return to normal watcli the lungs 

 closely and inject two cubic centimeters of ergamine solu- 

 tion (or less if the animal is small) and record the results. 

 How is the carotid pressure affected? Did you see any 

 change in the relative extent of expansion and contraction 

 of the lungs with each inflation from the respiration ma- 



