Jacob Jongbloed (nick-named "Janus ") was a Dutch aviation physiologist and avid aviator. While lack of funding hindered his work tremendously, he nonetheless became an important figure in aeromedical research between World War I and II, chiefly in the field of the effects of acceleration on the human organism. Most of his work was published in Dutch and German journals, rendering him an unknown force in the English-speaking world. Only after World War II did he make a name for himself in Anglo-American circles, primarily due to his involvement in various international organizations dealing with aeromedical matters and his part in developing the first Dutch heart-lung machine. Due to his many posts and his scientific work in the field, he could be regarded as the "father" of Dutch aviation medicine.