2. A man may do many acts which are justifiable or not, as he is ignorant or not ignorant of certain facts. He may pass a counterfeit coin, when he is ignorant of its being counterfeit, and is guilty of no offence; but if he knew the coin to be counterfeit, which is called the scienter, he is guilty of passing counterfeit money. A man who keeps an animal which injures some person, or his property, is answerable for damages, or in some cases he may be indicted if he had a knowledge of such animal's propensity to do injury. 3 Blackst. Comm. 154; 2 Stark. Ev. 178; 4 Campb. 198; 2 Str. 1264; 2 Esp. 482; Bull. N. P. 77; Burr. 2092; 2 Lev. 172; Lord Raym. 110; 2 B. & A. 620; 2 C. M. & R. 496; 5 C. & P. 1; S. C. 24 E. C. L. R. 187; 1 Leigh, N. P. 552, 553; 7 C. & P. 755.