The commission shall appoint the executive heads of all state institutions and facilities under the supervision of the state department, and such assistants and employees for them and the state department, and may incur such other expenses as may be necessary to carry out the provisions of this act. The executive head of each state institution under the supervision of the state department shall be responsible for the employment of all assistants and employees thereof. The compensation of all such assistants and employees, and the number thereof, shall be within the appropriations made therefor by the legislature. Such assistants and employees shall receive their actual and necessary traveling and other expenses incurred in the discharge of their official duties. All salaries and expenses shall be paid in the same manner as the salaries and expenses of other state employees are paid.