LXIV.] PERFUSION THROUGH BLOOD-VESSELS. 



307 



(c.) Make a snip in the sinus venosus or venae cavse to let the 

 fluid run out. Hang up the frog on a suitable holder. Take the 

 clip off the pressure tube, allow the normal saline, or Ringer's fluid, 

 to run into the blood-vessels and to wash out all the blood, until 

 the saline runs clear from the veins. Collect the outflow in a 

 funnel which is placed in a graduated measure. 



(<7.) After the Ringer's fluid runs clear, collect, measure, and 

 record the amount, when it is constant, every five minutes. 



(e.) Substitute normal saline or Ringer's fluid, to which some 

 'drug lias been added, and perfuse it. Note the effect. If there is 

 an increased outflow, the blood-vessels, chiefly the arterioles, have 

 been dilated. If less, they have been contracted. Record the 

 results, and if necessary make a chart to show the result. 



The water-tortoise is a very convenient animal to use, the perfusion cannula 

 being fixed in the third or fourth aorta, the others being tied. It is con- 

 veniently placed in a glass funnel when perfusion is being carried on. 



In the frog, after a time, there is considerable oedema of the lymph-sacs. 



It is most important that the student should keep notes of his results. From 

 the results obtained, plot a curve on paper divided into squares. Make the base 

 line represent time, and the vertical lines, or ordinates, the amount of outflow. 



Some substances greatly contract the blood-vessels, e.g., very 

 dilute nitric acid, and extract of the suprarenal capsules. The 

 latter is specially powerful in constricting the arterioles. (Schdfer 

 $ Oliver.) Others dilate, the vessels, especially the nitrites, 



PERFUSION EXPERIMENTS. 



