In any proceeding for the enforcement of a claim for compensation under this chapter it shall be presumed, in the absence of substantial evidence to the contrary—
That the claim comes within the provisions of this chapter.
That sufficient notice of such claim has been given.
That the injury was not occasioned solely by the intoxication of the injured employee.
That the injury was not occasioned by the willful intention of the injured employee to injure or kill himself or another.
(Mar. 4, 1927, ch. 509, § 20, 44 Stat. 1436.)