This appears to be all we know about "M. B. Smith," credited with authorship of "The Battle of Shiloh's Hill." Presumably there was only one "M. B. Smith" in Co. C, 2nd Texas:

"Fold 3 has records for Mirabeau Smith. He enlisted August 13, 1861 as a private in Company C of the 2nd Regiment of Texas Infantry. He went into the hospital at Galveston that September and was diagnosed with 'Hydro Cirr [sic] Carditis with deranged Val [sic]' which appears to be a form of cardiac disease. He was back in the hospital in December with a fever. He returned in January suffering from deafness. He appears to have been discharged from the army in June, and with that medical record it's no surprise."


https://civilwartalk.com/threads/m-b-smith.214135/

The 2nd Texas was raised at Galveston. "Hydro Cirr Carditis" doesn't appear anywhere on the 'Net. Any form of carditis would have been very serious in 1861 (if correctly diagnosed).