2. It is a general rule, established for the purpose of shortening and facilitating investigations, that the point in issue is to be proved by the party who asserts the affirmative; 1 Phil. Ev. 184; Bull N. P. 298; but as this rule is not founded on any presumption of law in fav-or of the party, but is merely a rule of practice and conveience, it, ceases in all cases when the presumption of law is thrown into the opposite scale. Gilb. Ev. 145. For example, when the issue is on the legitimacy of a child born in lawful wedlock, it is, incumbent on the party asserting its illegitimacy to prove it. 2 Selw. N. P. 709. 3. Upon the same principle, when, the negative averment involves a charge of criminal neglect of duty, whether official or otherwise, it must be proved, for the law presumes every man to perform the duties which it imposes. 2 Gall. R. 498; 19 John. R. 345; 10 East, R. 211; 3 B. & P. 302; 3 East, R. 192; 1 Mass. R. 54; 3 Campb. R. 10; Greenl. Ev. SS 80; 3 Bouv. Inst. n. 3089. Vide Onus Probandi.