Online text collections (historical newspapers, immigrant letters or historical photographs) are PRIMARY SOURCES. Primary sources have been generated within the time period you are studying, and most have been originally in print (news articles, photos, pamphlets).
JSTOR is included in this list because journal articles from medical journals published in the 1920 through 1950s are primary sources as well. They give us insights on how a disease like tuberculosis was understood by the medical establishment at the time.
There are many archives collections within the Golden Horseshoe area, but you will not have time to consult them in person. Instead, here you will find those few links you may access at the UTM Library.
Here is an example of a journal that might have relevant articles on the evolution of TB treatment over the years. It can help you with the context for your research.
Medical texts and histories make fine primary sources. Most of the books you will find in the system are in print at Gerstein, but if you request these via Document Delivery service (through the Request link in the catalogue), it will take only two business days to get them to UTM.