This article details the collaboration between Dr Walter B. Cannon (1871-1945) and Dr Arturo Rosenblueth (1900-1970) at the Department of Physiology at Harvard Medical School (HMS) in the 1930s-1940s. Cannon was a renowned physiologist whose Department of Physiology was home to scientists from around the globe. Rosenblueth joined the Department as a Research Fellow in 1930. Over the following 15 years, Rosenblueth and Cannon co-authored over 20 papers and one book. Rosenblueth ended his tenure at HMS as an assistant professor before returning to Mexico to head a newly created institute of physiology. This article draws from personal and professional correspondences between Cannon and Rosenblueth at HMS in the 1930s and early 40s. These letters, along with others from those at the Department of Physiology and the greater Harvard community paint a picture of the feeling towards Latin American scientists at that time. Finally, this brief survey illuminates some of the contributions of the many Latin American scholars who worked in the department during these years. The diverse backgrounds of these talented young scientists coupled with immense support from Cannon and Rosenblueth enabled remarkable discoveries and innovations in neurophysiology throughout the first half of the 20th century.