1. The evidence authorized the verdict, and the errors complained of are not of sufficient materiality to require the grant of a. new trial.

2. Evidence which is sufficient to rebut the presumption of negligence may itself be discredited by proof of physical facts and circumstances which show such testimony to be incredible. Western & Atlantic R. Co. v. Clark, 2 Ga. App. 346 (58 S. E. 510) ; Atlantic & Birmingham Ry. Co. v. Clute, 3 Ga. App. 508 (60 S. E. 277).

3. Any witness may give his opinion, after having given the facts upon which he bases it, so as to enable the jury to determine the probative-value of his -opinionative evidence. The value of services rendered maybe proved in this way. Judgment affirmed.