¶1A motion for a rehearing was made by the defendant in error, and it was urged that the case of Boyle v. State, 57 VVis. 472, is clearly distinguishable from this case. The question here is not whether an expert witness may testify as to what an author says, but whether a person may become an expert on any given subject by close attention and discriminating study of that subject, together with practical experience in a profession of which that subject is a part. That a witness may testify from knowledge so acquired, see, besides cases cited on the former argument, Tullis v. Kidd, 12 Ala. 648; State v. Terrell, 12 Rich. 321; Bierce v. Stocking, 11 Gray, 174; State v. Baldwin, 36 Kan. 1-16: The extent of the special knowledge to be required of an expert is so much a matter of discretion with the trial court that its decision should be disturbed only when the witness is shown to be wholly incompetent. Ardesco Oil Co. v. Gilson, 63 Pa. St. 146; Spring Co. v. Edgar, 99 U. S. 645-648; Tucker v. M. C. R. Co. 118 Mass. 546; Nelson v. Sun Mut. Ins. Co. 71 N. Y. 453; Ft. Wayne v. Coombs, 107 Ind. 75; Warren v. Spencer Water Co. 143 Mass. 9; Perkins v. Stickney, 132 Mass. 217; Howard v. Providence, 6 R. I. 514; Bemis v. C. V. R. Co. 58 Vt. 636; Best on Evi. (Morgan’s Notes), sec. 513, p. 868, note 3, p. 876, note 1, and p. 882, per Miller, C. J.
¶2Counsel for the plaintiff in error cited, besides cases previously cited by them, Polk v. State, 36 Ark. 117; Bouvier’s Law Dict. tit. Expert; Nelson v. Sun Mut. Ins. Co. 71 N. Y. 460.
¶3The motion was denied December 22, 1888.