4. "May presume".- Whenever it is proved by this Act that Court may presume a fact, it may either regard such fact as proved, unless and until it is disproved, or may call for proof of it.

"Shall presume".—whenever it is directed by this Act that the Court shall presume a fact, it shall regard such fact as proved, unless and until it is disproved.

"Conclusive proof.—When one fact is declared by this Act to be conclusive proof of another, the Court shall, on proof of the one fact, regard the other as proved, and shall not allow evidence to be given for the purpose of disproving it.