The term “secretary” wherever used in this chapter shall mean the secretary of health of the state of Washington. The term “apprentice” wherever used in this chapter shall mean a person who shall be designated an apprentice in the records of the secretary at the request of a physician, registered optometrist, or licensee hereunder, who shall thereafter be the primary supervisor of the apprentice. The apprentice may thereafter receive from a physician, registered optometrist, or licensee hereunder training and direct supervision in the work of a dispensing optician.