Felix Bloch was a lifelong friend from early days in Switzerland. He later moved to America and settled at Stanford. He was awarded the Nobel Prize in 1952.
The letter are mainly personal, Bloch's letters addressing Bretscher as 'Gon'; letters of 1930 are from Bloch in hospital, and from Bloch's mother, both referring to the mountaineering accident in August when Bloch broke a leg and Bretscher contributed largely to saving his life when they had to spend two nights in the open