2 A suspension bottle is filled with cold saline, and an infusion needle is inserted into the left ventricle (at the apex) to open the infusion valve.
3 A small cut is made in the right atrium to allow blood and lavage fluid to drain.
4 After about 50 ml of saline has been instilled, observe that the fluid coming out of the right atrium has become colorless and transparent, indicating that the blood has been flushed out.
5 Do not remove the infusion needle from the heart and continue the infusion with a different vial containing pre-cooled 4% paraformaldehyde. Mice will convulse violently when paraformaldehyde is introduced into the body.
6 After the convulsions stop, and then continue to infuse 5 minutes, paraformaldehyde can be fully immobilized in the body of the mouse organs, pulling the limbs with a sense of stiffness. At this time, the fixation has been completed and can be taken.