At the end of the nineteenth century, studies in bacteriology underwent great development. The use of photomicrographs as illustrations of Atlas and reports on bacteriology had a key role in the transmission of scientific knowledge in this field. This was partly due to the improvement of histological techniques and the reliability of scientific photography.
On July 1899, the city of Porto in Portugal was hit by an outbreak of the third pandemic of the bubonic plague. To determine the nature of this disease, bacteriological analyses and microscopic preparations of the bacillus were carried out under the direction of Ricardo Jorge, professor at the Medical School. Photomicrographs illustrate the report sent by him to the Portuguese health authorities. Portuguese medical dissertations and reports on the plague, published in this period, were also illustrated with photomechanical prints of photographs and photomicrographs obtained with the collaboration of professional photographers established at Porto, such as Emilio Biel. In 1908 there was another outbreak of the plague at the archipelago of the Azores, mainly in the islands of Terceira and Faial. Microscopic preparations of the bacillus were photographed at the Microbiological Laboratory at Porto but only at the end of 1908 was a medical mission sent to the Azores, so the difficult task of diagnosis and possible treatment of patients was ensured by the local medical doctors of the islands.
In this communication we examine the role of photography as a scientific document in the case of the bubonic plague outbreaks that occurred in Portugal.