45-108.Interest; rate; when calculated by the year.When in any law, or in any instrument in writing specifying a rate of interest, no period of time is mentioned for which such rate is to be calculated, it shall be deemed to be by the year.SourceLaws 1879, § 9, p. 115; R.S.1913, § 3354; C.S.1922, § 2842; C.S.1929, § 45-109; R.S.1943, § 45-108.