Figure 1. Testis collection.

A. Place the sacrificed mouse on its back, wet the skin of the abdomen with 70% ethanol, and open the skin of the lower part of the abdomen with a small cut using scissors. Pinch the skin between the fingers of each hand just above and below the small cut and pull up and downward (along the anterior-posterior axes) to tear the skin further and visualize the peritoneum. This helps to avoid hair contamination. B. Use a tweezer to grasp the peritoneum and use a scissor to cut it open and to enlarge the opening laterally. C. The organs in the lower part of the abdominal cavity are visible at this point (intestine and bladder). The testis is descended and located in the scrotum. Most often, they are not yet visible. To retrieve them from the scrotum, use tweezers to grasp adipose tissue on either side of the bladder and softly pull each of them upwards. D. This will expose the testis, visible as an egg-shaped tissue that should be separated from the surrounding tissue such as the epididymis, blood vessels, etc., using tweezers and scissors to carefully isolate it.