3o6 



PRACTICAL PHYSIOLOGY. 



[lxiv. 



just killed. Expose the vagus rapidly, open the chest and observe the heart 

 beating, or thrust a long needle through the unopened chest in the heart, then 



on stimulating the peripheral 

 end of the vagus with an inter- 

 rupted current the movements 

 of the heart are arrested for a 

 short time — the heart itself 

 being in diastole. 



7. Effect of Swallowing on 

 the Heart (p. 312). 



8. B. P. in Man v. Baach's 

 Sphygmomanometer. — Tliis 

 consists of a brass capsule 

 covered on its open end with 

 sheets of caoutchouc, and con- 

 nected by means of a tube 

 with a manometer constructed 

 on the principle of an aneroid 

 barometer. It is best to 

 apply it to the superficial 

 temporal artery, as there is a 

 bony supj)ort behind that. 



One compresses the artery until the pulse beyond is obliterated, and then 

 reads off directly the pressure required to do this. 



FlO. 230— Improved Form of Arterial Cannula, by 

 frail Qois-Frank. A is tied into the artery ; B is 

 attached to the lead tube of the manometer : 

 and C, the lateral tube, is closed with an elastic 

 (damped) tube. 



LESSON LXIV. 

 PERFUSION THROUGH BLOOD-VESSELS. 



Perfusion through Blood- Vessels. — By perfusing fluids through 

 the blood-vessels of the body as a whole, or by perfusing blood 

 or other fluids through isolated " surviving " organs, much may be 

 learned regarding the action of drugs and other conditions on 

 the blood-vessels. The blood-vessels of the frog and tortoise, the 

 excised kidney, and other organs have been used for this purpose. 



Perfusion through Blood-Vessels of Frog. 



(a.) Pith a frog, expose its heart, snip one aorta, and allow the 

 blood to flow out. Previously a fine glass cannula with a shoulder 

 on it must have been prepared. Tie the cannula into one aorta, 

 and let the hgature also include the other aorta. 



(b.) Attach the cannula to an india-rubber tube containing normal 

 sahne and connected with a glass funnel filled with normal saline 

 and held in a suitable holder, e.r/., a ring on a retort stand, placed 

 about 6-7 inches above the heart. See that there is no air in the 

 connections, and that the cannula is filled with normal saline by 

 means of a fine pipette before it is connected up with the pressure 

 tube. Put a cHp on the pressure tube. 



