Between 1874 and 1877, Roux received a fellowship for the Military School at Val-de-Grâce, but quit it after failing to present his dissertation in due time.

[8] According to his niece, Roux allegedly believed that marriage was an opportunity for women to satisfy their "deepest aspirations", while for men it was "mutilation".

They also held different religious and political beliefs, with Pasteur being a right- leaning Catholic, and Roux being a left-leaning atheist.

[4] In 1883, he presented a doctoral dissertation in medicine titled Des Nouvelles Acquisitions sur la Rage, in which he described his research on rabies with Pasteur since 1881, which led to the development of the first vaccination against this fearsome disease.

[11][1] The development of a diphtheria anti-toxin serum was a race between researchers Emil Behring in Berlin, and Émile Roux in Paris.

[12] The race to develop the diphtheria anti-toxin serum was considered a national rivalry, although each team of researchers adopted each other's experimental practices and built off of each other.

[13] In a controversy, the first Nobel Prize for Physiology and Medicine was given to Emil Von Behring for his work on the serum therapy for diphtheria.

[14] Also in 1883, Roux published, with Alexandre Yersin, the first of his classical works on the causation of diphtheria by the Klebs-Loeffler bacillus, then an extremely prevalent and lethal disease, particularly among children.

Diphtheria is contagious microbial disease marked by throat lesions, polyneuritis, myocarditis, low blood pressure, and collapse.

He successfully demonstrated the use of this antitoxin with Auguste Chaillou in a study with 300 diseased children in the Hôpital des Enfants-Malades and was henceforth hailed as a scientific hero in medical congresses throughout Europe.

[1] In the following years, Roux dedicated himself indefatigably to many investigations on the microbiology and practical immunology of tetanus, tuberculosis, syphilis, and pneumonia.