I looked up Corporal Donaldson on the online Missouri State Archives military service records at the MO Sec'y of State website. I don't know where you got the "National" part. Corporal James Donaldson enlisted in Captain Frederick R. Neet's Company K of the 14th Regiment Home Guard at Lexington 12 August 1861. I never heard of this regiment before looking it up for you. You see, I deal mostly in "irregular" guerrilla warfare in Missouri and not in this "regular" stuff, especially during 1861. During 1861 a large number of northern "ad hoc" or unofficial home guard units popped up across Missouri and many performed valiant service until they were ordered disbanded in the winter of 1861/1862 by the larger Union command. Donaldson (and most of his unit) surrendered to the southern Missouri State Guard at the conclusion of the seige of Lexington 20 September 1861. As a parolee he was sent (along with the others) to be kept in a parolee camp at St. Louis where he was mustered out of service 19 October 1861.
I don't know if he performed any other service during the war, but a Private James Donaldson enlisted 22 August 1862 at St. Joseph in Captain Hyde's Company H of the 35th Missouri Infantry Regiment. This man died of disease 10 November 1863 at Helena, AR. I don't know if this is YOUR James Donaldson.
I hope that helps. It's a little outside of my area or research, so I hope I didn't goof it up too much for you.