Henry Beecher was indeed one of the outstanding physicians of the mid-20th century. For the last several years, he worked on a history of the Harvard Medical School, but he died while the work was still in progress. Mark Altschule, Beecher's classmate, also a fruitful investigator and prolific author, undertook to complete the work. Those acquainted with Altschule's writings will find many passages that bear the unmistakable stamp of his prose—witty, terse, but not always reliable when it asserts opinion as fact. I would guess that Beecher laid out the plan of the whole, wrote most of the first two parts, much of the third, and portions of the last, while Altschule revised the whole and, I would imagine, contributed heavily to the latter part of the book.
The Harvard Medical School had its formal beginning in 1782, but the whole period from earliest colonial medicine to 1869 is compressed
King LS. Medicine at Harvard: The First 300 Years. JAMA. 1977;238(16):1766. doi:10.1001/jama.1977.03280170060035