§ 21. Presumptions. 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

1. That the claim comes within the provision of this chapter;

2. That sufficient notice thereof was given;

3. That the injury was not occasioned by the willful intention of the
injured employee to bring about the injury or death of himself or of
another;

4. That the injury did not result solely from the intoxication of the
injured employee while on duty.

5. That the contents of medical and surgical reports introduced in
evidence by claimants for compensation shall constitute prima facie
evidence of fact as to the matter contained therein.