Militia officers shall be chosen or appointed as follows: Captains, subalterns and non-commissioned officers shall be chosen by the written votes of the members of their respective companies. Field officers of regiments and separate battalions by the written votes of the commissioned officers of the respective regiments and separate battalions; brigadier-generals and brigade inspectors by the field officers of their respective brigades; major-generals, brigadier-generals and commanding officers of regiments or separate battalions, shall appoint staff officers to their respective divisions, brigades, regiments or separate battalions.