This chapter shall not apply to the commissioned surgical officers of the United States Army, Navy or Marine hospital service when in the actual performance of their official duties, nor to any physician duly registered, nor to any legally registered podiatrist of another state, taking charge of the practice of a legally registered podiatrist of this state temporarily during the latter’s absence therefrom upon the written request to the board of said registered podiatrist of this state. This chapter shall further not apply to manufacturers of and dealers in shoes or corrective appliances for deformed feet; provided, however, that such manufacturers and dealers shall not be entitled to practice podiatric medicine, as in this chapter defined, unless duly licensed so to do as herein provided.