The introduction of projection of photographic light images in academic teaching in the Netherlands was a fitting response to the increased number of students in the late 19th century: while the professor was explaining, everyone saw the same illustration material. Moreover, image projection allowed more examples to be shown in a shorter time frame. This thesis focuses on the role of the optical lantern in knowledge transfer at Dutch universities between 1880 and 1940. To interpret the different roles of projection, I chose to examine three academic disciplines: botany, art history and dentistry. These disciplines all represent a specific "thought collective". In the words of science philosopher Ludwik Fleck's this represents a community of people who exchange ideas among themselves and maintain a certain intellectual interaction. One important basis of a "thought collective" concerns academic education, as it contributes to both the formation and continuity of the community. Therefore, this research considers lectures with projected images as an intrinsic part of the training of new generations of scientists. This creates a new connection between the subfields of university history and history of science. Accordingly, this research into daily teaching practice by means of projected slides allows us to gain a better understanding of the different focal points of knowledge transfer, of the relationship between textbooks and lectures and between theory and practice. The enormous quantities of glass slides still to be found in the various archive repositories today offer an excellent opportunity for research into the relationship between teaching practice and science communication.