What is the principle when the plaintiff is under no legal duty to affect the rescue?

The principle is the same when the plaintiff is under no legal duty to effect the rescue if one person by his negligence causes another to be in a position of danger he should have regard to the probability that a third person, acting bravely and promptly and subjugating any timorous over concern for his own well being or comfort may attempt a rescue. No distinction appears to be drawn between the rescuer who acts instinctively and one who takes time for reflection before he encounters the risk.