He was more distinguished as a man of science than as a politician or administrator. His classical work,
La Pression barometrique (1878), embodies researches that gained him the biennial prize of 20,000 francs from the Academy of Sciences in 1875, and is a comprehensive investigation on the physiological effects of air-pressure, both above and below the normal. Central nervous system
oxygen toxicity was first described in this publication and is sometimes referred to as the "Paul Bert effect". He showed that oxygen was toxic to insects,
arachnids,
myriapods, molluscs, earthworms, fungi, germinating seeds, birds, and other animals. He also received the
Cameron Prize for Therapeutics of the University of Edinburgh in 1879 for this work. His earliest researches, which provided him with material for his two doctoral theses, were devoted to animal grafting and the vitality of animal tissues, and they were followed by studies on the physiological action of various
poisons, on
anaesthetics, on
respiration and
asphyxia, on the causes of the change of color in the chameleon, etc. He was also interested in vegetable physiology, and in particular investigated the movements of the sensitive plant, and the influence of light of different colours on the life of vegetation (
photobiology). He wrote a very successful textbook with
Raphael Blanchard,
Éléments de zoologie G. Masson (Paris), 1885. In
The Phrenological journal and science of health (1883) it was claimed that he held an atheistic belief. ==Racist theories==