The separate negligent acts of the defendants must concur to cause a single injury which would not have happened but for the concurrence of the defendants' acts. Both will then be held liable.
Where separate acts of negligence combine to contemporaneously to produce directly a single injury each tort-feasor is responsible for the entire result, even though his act alone might not have caused it (Hancock v. Steber, 208 App. Div. 455; Matthews v. State of New York, 271 App. Div. 389, affd. 296 N. Y. 946).
'Where two or more persons are guilty of separate acts of negligence which in point of time and place concur, and together proximately cause injury to another, they are guilty of concurrent negligence for which they may be held jointly and severally liable in an action by the injured person or, in case death results therefrom, by his personal representative.' Reilley v. Byard, 146 W. Va. 292, 119 S.E.2d 650 (1961).