1. The rule of res ipsa loquitur is not a substantive rule of law. It is rather a rule' of evidence, which permits the jury, but not the court in a jury trial, to draw an inference of negligence where the instrumentality causing the injury is under the exclusive management and control of one of the parties and an acci•dent occurs under circumstances where in the ordinary course of events it would not occur when ordinary care is observed. It is an evidential inference, not controlling upon the jury but to be considered by the jury under proper instructions. A like inference under like circumstances may be drawn by the court when the court is the trier of the facts.

2. Where the allegations in a petition and the evidence offered in support thereof call for the application of the rule of res ipsa loqui-tur, and where the defendant has offered evidence tending to meet and explain the circumstances, it is the duty of the court, when requested so to do by either party, to submit the question to the jury under proper instructions.

3. The weight of the inference' as well as the weight of the explanation offered to meet the inference is for the determination of the jury in a jury trial or for the determination of the court when the court is the trier of the facts.

Judgment reversed.