Samuel McCallum of New York was a student in the Medical Department at the University of the City of New-York (1878-1879). According to the "University of the City of New-York Medical Department Annual Announcement of Lecturers and Catalogue" (Session 1879-1880), he was under the instruction of Dr. W.F. Lindsay. He graduated in 1879 with a specialization in heart sounds. "The Announcement of Lecturers and Catalogue" also noted that the Medical Department graduate class of 1879 was the largest graduating class since the founding of the College in 1841.
From the guide to the Samuel McCallum Papers, 1878-1879, (New York University Archives)