In 1885 he received his medical doctorate in Paris and from 1891 performed scientific research in Lille. In 1896 he became a professor of histology.
Laguesse is remembered for his histopathological work involving the pancreas. In 1893 he named the small cellular clusters of the pancreas the "Islets of Langerhans", in honor of their discoverer Paul Langerhans (1847-1888). At the time of their discovery, Langerhans provided an excellent description of the structures, but offered no further conclusions as to their function. Laguesse postulated that the Islets of Langerhans produced secretions that played a regulatory role in digestion. Laguesse's research was considered a major step on the path of discovery of a new hormone in the early days of endocrinology.