In Healy v. Visalia etc. R. R. Co. (1894) 101 Cal. 585, the plaintiff was injured when the railroad handcar in which she was traveling jumped the track, threw her out of the vehicle, and ran over her. (Healy, supra, at pp. 588-589.) The jury returned a verdict for the plaintiff, and the defendant appealed, contending that another passenger should not have been allowed to answer the following question: " 'Under the circumstances, was it possible for an ordinary person, sitting in the position Mrs. Healy was sitting in, to stand the force of the jars and still retain her seat upon the car?' " (Id. at p. 589.) The court disagreed: "This question does not fall within the rule which excludes the opinion of a witness. The general rule is that the testimony of a witness shall be limited to the facts of which he has a personal knowledge, and that he shall not give his individual opinion thereon; but in many instances the opinion of a witness may be received in connection with his statement of the facts upon which it is based. The border line between fact and opinion is often very indistinct, and the statement of a fact is frequently only an opinion of the witness. Impressions or sensations caused by external objects are not susceptible of exact reproduction or description in words, nor do they affect every individual alike, and the judgment or opinion of the witnesses by whom they have been experienced is the only mode by which they can be presented to a jury. The question asked of the witness in the present case did not call for an opinion from him depending upon facts which he had subsequently learned, but he was asked to describe the effect of the concussion or jar caused by the car leaving the track, as one of the facts out of which the injury had arisen, and which he had personally observed and felt. The position of the plaintiff on the car, as well as his own position thereon, the jumping of the car from the track, the effect produced upon himself, the sensation which he experienced thereby, were all facts which it was competent to show by his testimony, in order that the jury might get as clear an idea as possible of the circumstances under which the accident had occurred. The strength or force of this concussion was also a fact which it was proper to bring before the jury, and as it was not capable of exact measurement by any recognized standard, it was competent for the witness to state its strength or force according to the opinion or judgment which he formed at the time that he felt it. His judgment or opinion of its effect upon an ordinary person would be the most efficient mode of enabling the jury to fully appreciate it, and to give to it its proper consideration in determining its influence in producing the injury. Such testimony is competent upon the same principle that permits evidence showing the strength or force of a blow, the distance at which a sound can be heard, or the direction from which it comes, the speed of a horse, the degree of cold or heat, or of light or darkness. In any such instance a witness who had a personal experience or knowledge of the sensation is competent to testify, although his answer is only his opinion of the matter. The accuracy or strength of his testimony is to be tested by cross-examination. These observations apply also to the testimony of the witness that he thought that the car was too narrow for the track, and also to the testimony of another witness, as to the appearance of the plaintiff immediately after the accident." (Id. at pp. 589-590.)