. An elementary course of practical zoology. Zoology. THE FROG CHAP. art abdomen of a freshly-killed frog in the usual way, taking great care not to injure the blood-vessels. Remove the middle portion of the shoulder-girdle so as to expose the heart, lay open the pericardium, and with a single snip of the scissors cut off the pos- terior half of the ventricle, allowing the blood to escape freely. Pass a piece of thread (not cotton), about six inches long, round the heart, at about the junction of the auricles and ventricle, and give it a single loose tie, as shown in Fig. 25. When the bleeding
. An elementary course of practical zoology. Zoology. THE FROG CHAP. art abdomen of a freshly-killed frog in the usual way, taking great care not to injure the blood-vessels. Remove the middle portion of the shoulder-girdle so as to expose the heart, lay open the pericardium, and with a single snip of the scissors cut off the pos- terior half of the ventricle, allowing the blood to escape freely. Pass a piece of thread (not cotton), about six inches long, round the heart, at about the junction of the auricles and ventricle, and give it a single loose tie, as shown in Fig. 25. When the bleeding has ceased, fill the medicine dropper, or syringe, with injec- tion-mass and pass the narrow end of the former, or the nozzle of the latter, through the cut end of the ventricle into the conus —take care not to push it into one of the auricles instead—and tighten the thread so as to keep it in place. Then squeeze the cap of the medicine dropper, or push in the piston of the syringe, and if the operation is successful, you will see the blue injection pass from the conus into the arterial trunks, and thence into the various arteries of the body. The contrast between the arteries, filled with the blue mass, and the veins, filled with blood, is then very striking, particularly in the mesentery. When the arteries are well-filled, withdraw the nozzle from the heart and instantly draw the thread tight and knot it so as to prevent escape of the injection. Then place the whole frog in spirit (methylated spirit 3 parts, water I part), for a few hours, after which time the injection mass will be found to have set hard enough to allow of the arteries being conveniently traced. Injection of the Veins.—The veins are much more difficult to inject tlian the arteries, but if you wish to make a double injection on the same specimen, colour the injection-mass with vermilion or carmine. Fig. 23.—Sketch showing the method of injecting the frog's arteries. «. glass " medicine-dropper'
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1900
