There are two questions raised by this appeal. First, does plaintiff’s evidence, when considered in the light most favorable to him, make out a prima facie case of negligence on the part of the defendant? And second, does plaintiff’s evidence establish that the plaintiff was contributorily negligent as a matter of law?
[1-3] “Negligence is the failure to exercise proper care in the performance of a legal duty which the defendant owed the plaintiff under the circumstances surrounding them. (Citation omitted.) The breach of duty may be by negligent act or a negligent failure to act. *472(Citations omitted.)” Dunning v. Warehouse Co., 272 N.C. 723, 158 S.E. 2d 893. And “[p]ersons having possession and control over dangerous substances, machinery, and instrumentalities are under a duty to use a high degree of care commensurate with the dangerous character of the article, to prevent injury to others.” 6 Strong, N.C. Index 2d, Negligence, § 5, p. 10, 11. From the evidence in this case the jury would be justified in finding defendant negligent for failing to have the metal hood in place to cover the chain and sprocket mechanism. However, for defendant’s negligence to be actionable, it is necessary for the evidence to show that such negligence was a proximate cause of plaintiff’s injury.
“Proximate cause is a cause which in natural and continuous sequence, unbroken by any new and independent cause, produced the plaintiff’s injuries, and without which the injuries would not have occurred, and one from which a person of ordinary prudence could have reasonably foreseen that such a result, or some similar injurious result, was probable under the facts as they existed. (Citation omitted.) A proximate cause may involve an act or omission which does not immediately precede the injury or damage, and therefore, proximate cause and immediate cause are not synonymous. (Citation omitted.) There may be more than one proximate cause of an injury, and it is not required that the negligence of the defendant be the sole proximate cause of the injury or the last act of negligence in sequence of time in order to hold defendant liable therefor, it being sufficient if defendant’s negligence is one of the proximate causes. (Citation omitted.) Although foreseeability of injury is an essential element of proximate cause (citation omitted), the test of such foreseeability does not require that the tort-feasor should have been able to foresee the injury in the precise form in which it occurred. All that the plaintiff is required to prove on the question of foreseeability, in determining proximate cause, is that in the exercise of reasonable care the defendant might have foreseen that some injury would result from his act or omission, or that consequences of a generally injurious nature might have been expected. (Citation omitted.)” Grimes v. Gibert, 6 N.C. App. 304, 170 S.E. 2d 65.
 Applying these principles to the case at bar, plaintiff’s evidence and the legitimate inferences therefrom is sufficient to justify, but not compel, the jury in finding defendant was negligent and that its negligence was a proximate cause of plaintiff’s injury.
*473Defendant having pleaded plaintiff’s contributory negligence, we now consider the second question raised by this appeal.
Plaintiff’s evidence, being sufficient to require submission of the issue of defendant’s negligence to the jury, the judgment of involuntary nonsuit must be reversed unless plaintiff’s evidence discloses that he was guilty of contributory negligence as a matter of law. Dunning v. Warehouse Co., supra.
 Plaintiff’s evidence tends to show that, prior to his injury, he was not aware of the mechanism attached to the tailgate of the truck. The law does not require a person to shape his behaviour by circumstances of which he is justifiably ignorant and a plaintiff cannot be guilty of contributory negligence unless he acts or fails to act with knowledge and appreciation, either actual or constructive, of the danger of injury which his conduct involves. Clark v. Roberts, 263 N.C. 336, 139 S.E. 2d 593. Had plaintiff slipped and fallen under the wheel of the truck, thereby sustaining injury, such may present a different case. But plaintiff’s injury was due to his finger being caught in a chain and sprocket the existence of which he was unaware and which was not covered by the metal hood specifically designed to enclose the mechanism from the outside.
In our view plaintiff’s evidence does not establish contributory negligence as a matter of law. The nonsuit was improvidently granted.
BRItt and Graham, JJ., concur.