1． Remove one or two rat tails and greeze at -80C overnight
2． Thaw the tails （about 1/2 hour） and scrub the tail with septisol to kill any bacteria.
3． Rinse well with water.
4． Put the tail in a clean sterile 150mm Petri dish and cover with 80% ethanol.
5． Let it sit in the ethanol for at least 20 mins
6． Remove the tail and put into another Petri dish to dry off the ethanol.
7． While the tail is drying, prepare a 10% sterile acetic acid solution and pre weight a 60mm Petri dish containing about 3ml of sterile water.
8． While the tail has dried. Remove the tendons. With a hemostat grab the tail one inch from the step. Snap the tail just above the hemostat with a small bone cutter and pull the tendons out.
9． Cut the tendons and place in the Petri dish containing water.
10. After all the tendons are removed, weight the dish.
11 Subtract the per weight from the weight with the tendons and calculate the gram weight of your tendons.
12. Place the tendons in a bottle containing sterile 0.1% acetic acid. （250ml/1 gram tendon）.
13. Let this sit in the icebox for five days.
14. Remove the tendon slurry from the bottle and place in centrifuge tubes.
15. Spin the tubes for 1hour at 12000rpm 4C
16. Remove the supernatant and dialyze overnight against water to remove the acetic acid.
17. Aliquot into 10ml fractions and store in the icebox. The collagen is good for at least one month.