A record of all examinations shall be kept. Appointments to all positions under civil service shall be made by the board or officer having the power of appointment from a list of those who have taken examinations for such positions, and such appoint-ment must be made from the three holding the highest rating on such list. Persons appointed to permanent positions shall be on probation for a period of not less than one year before appointment or promotion is made complete, during which period a probationer may be discharged or reduced by the appointing board or officer. (Stats. 1927 p. 2095; Stats. 1938 p. 152).