Spreading out the fingers tests the integrity of which: i. Nerve -ii. Muscle group

The action of spreading out the fingers primarily tests the integrity of the nerve rather than a specific muscle group. Specifically, it assesses the function of the ulnar nerve, which innervates the interossei muscles of the hand responsible for finger abduction and adduction.

1. Nerve Integrity: The ability to spread the fingers properly indicates that the ulnar nerve is functioning correctly, as it controls the fine motor functions required for finger abduction.

2. Muscle Group: While the interossei muscles are involved in this movement, the test itself is more about the nerve's capacity to signal these muscles effectively, rather than solely examining muscle strength.

Therefore, the spreading of the fingers is primarily a test of nerve integrity, particularly relating to the ulnar nerve.