CHAPTER XXIII 

 Perfusion of Vessels. Lymph-Hearts 



Estimation of contraction or dilatation of vessels by measurement of 

 perfusion rate. Tie a small glass cannula, bent round so that its limbs 

 are parallel, into the aorta of a large frog killed by destruction of the 

 nervous system ; the cannula can either be passed directly into the cut 

 aorta or more easily through an incision in the ventricle. In exposing 

 the heart and aorta make as small an opening as possible. First 

 remove a flap of skin, then cut through the upper part of the ensiform 

 cartilage, and extend the incision on either side of the sternum : force 

 this up like a flap until the heart is sufficiently exposed. 



The cannula must be filled with Ringer's solution, and connected 

 through an india-rubber tube with a reservoir of the same fluid which 

 is allowed to drop slowly from it during the introduction ; this is for 

 the sake of excluding air bubbles. 



Suspend the frog by a pin through the jaw, and fix the reservoir a 

 short distance above the head so that the fluid flows into the vessels 

 by gravitation. Make a cut into the sinus venosus to enable the fluid 

 to flow freely out after it has traversed the blood-vessels of the body ; 

 the escaping fluid will drip from the toes, which should be tied together. 

 A cut must be made through the skin of each foot to prevent accumu- 

 lation* in the lymph-spaces of the legs. Count the number of drops 

 per minute, and repeat the counting twice ; after the blood is com- 

 pletely washed out the flow should be fairly regular. 



To test the effect of drugs or reagents upon the muscular tissue of 

 the arterioles the reagent is added in known quantity to the perfusing 

 fluid. The Ringer's solution to which the drug is to be added is placed 

 in a second reservoir, as in perfusion of the frog heart (see Fig. 63, 

 p. 75). Again count the number of drops per minute (three estimations), 

 and thus determine whether the arterioles are becoming dilated or 

 contracted as the effect of the reagent. This experiment may be tried 

 with Ringer's solution containing acid (HC1, 1 in 5,000) and alkali 

 (NaOH, 1 in 5,000), with a very dilute extract of suprarenal, with 

 barium chloride, and with solutions of chloroform and ether in Ringer's 

 solution. Normal Ringer's solution must invariably be substituted 



