The experimental method was obtained from the official website of the Fourth Military Medical University
Operation method
Experiments on the preparation of isolated frog heart specimens
Materials and Instruments
Frog Move (1) Exposure of the frog's heart: a toad is taken, the brain and spinal cord are destroyed, and the toad is fixed supine on a frog board. The skin of the thorax was cut upward or cut off from under the raphe, and then the sternum was cut off to open the pericardium and expose the heart and arterial trunk.(2) Observe the anatomy of the heart: a ventricle can be seen on the ventral surface, above which there are two atria, and an arterial trunk is attached to the upper right corner of the ventricle, which expands into an arterial cone at its root, also known as the arterial bulb. The artery can be divided upward into two branches, right and left. With a glass needle from the back of the arterial trunk through the heart turned to the side of the head, in the back of the heart under the two atria, can be seen in the color of the purplish-red dilated part of the heart for the venous sinus, which is the starting point of the amphibian heart, to observe the venous sinus, atria, ventricles contraction between the sequential relationship (Figure 1). Caveat (1) Do not injure the venous sinus when preparing the frog heart specimen.(2) The fluid level in the frog heart cannula should be maintained at the same level during each fluid change.(3) Add drops of Ren's solution to the surface of the heart at any time to keep it moist. For more product details, please visit Aladdin Scientific website.
Frog plate Small glass plate Coarse scissors Straight scissors Large tweezers Small tweezers Ophthalmic scissors Probe needle Glass minute needle Large beaker Small beaker Dropper Petri dish Cotton thread Ren's solution Zinc-copper fork
Figure 1(3) Cardiac intubation: use silk thread to ligate the right aorta, right and left pulmonary artery, anterior and posterior vena cava, or wrap a silk thread around the bottom of the heart to ligate the above blood vessels, but this ligation should be especially careful not to damage the venous sinus, so as not to cause cardiac arrest. When ligating, the frog heart clip can be used to clamp the tip of the heart during the diastolic phase, lift the heart connection, and then ligate clearly. To prepare for intubation, thread a wire under the left aorta, tie a loose knot, and use ophthalmic scissors to make a diagonal incision in the left aorta toward the heart (be sure to cut through the inner lining of the artery) to allow as much blood as possible to flow out of the heart (so that the blood does not clot after intubation). After flushing out the blood with Ren's solution, the frog heart cannula with Ren's solution was inserted into the left aorta, slightly withdrawn after inserting it into the aortic bulb, and then inserted the cannula along the posterior wall of the aortic bulb toward the center of the ventricle, and then inserted into the ventricular cavity through the aortic valve. At this time, the fluid level in the cannula can be seen to move up and down with the heart beat. The pre-tied loose knot was tied tightly and the thread was fixed to a small glass hook on the wall of the cannula to prevent slipping, the fluid in the cannula was aspirated with a dropper and replaced with fresh Ren's fluid, the cannula and the heart were lifted up carefully, and the heart was dissociated by cutting off the blood vessels and all the involved tissues below the above mentioned vascular ligature. At this point, the isolated frog heart was successfully prepared and ready for experimentation (Fig. 2). 
Figure 2