Louis Pasteur was a French chemist and microbiologist. Despite his modest upbringing, Louis Pasteur would eventually become France’s leading scientific mind and later be known as one of history’s most prolific geniuses. Pasteur’s greatest discoveries resulted in what he termed, “The Germ Theory of Disease” and led to breakthroughs in the causes and preventions of disease, methods of preservation and sanitary production of food. His work opened the door to further discoveries in Microbiology, Bacteriology and Chemistry in general.

Louis Pasteur's Childhood and Youth

Louis Pasteur was born on December 27, 1822 in the tranquil town Dôle, in the Jura region of France to the family of a poor tanner. Pasteur’s early education was not in life sciences, but rather he gained degrees in Letters and Mathematical Sciences. Pasteur was a novice artist and painted a series of pastel portraits, now collected under the title Pasteur: Dessins et pastels. As a young man Pasteur's father would share his experiences and opinions of the Napoleonic Wars. Later in life these shared memories would help Pasteur develop a great sense of pride and dedication to his homeland France.

Originally published in Modern Development of the Chemical and Biological Sciences Vol. 4 in 1904.

When Berzelius first promulgated his binary theory he was careful to restrict its unmodified application to the compounds of the inorganic world. At that time, and for a long time thereafter, it was supposed that substances of organic nature had some properties that kept them aloof from the domain of inorganic chemistry. It was little doubted that a so-called "vital force" operated here, replacing or modifying the action of ordinary "chemical affinity." It was, indeed, admitted that organic compounds are composed of familiar elements -- chiefly carbon, oxygen, hydrogen, and nitrogen; but these elements were supposed to be united in ways that could not be imitated in the domain of the non-living. It was regarded almost as an axiom of chemistry that no organic compound whatever could be put together from its elements--synthesized--in the laboratory. To effect the synthesis of even the simplest organic compound, it was thought that the "vital force" must be in operation.

Therefore a veritable sensation was created in the chemical world when, in the year 1828, it was announced that the young German chemist, Friedrich Wöhler, formerly pupil of Berzelius, and already known as a coming master, had actually synthesized the wellknown organic product urea in his laboratory at Sacrow. The "exception which proves the rule" is something never heard of in the domain of logical science. Natural law knows no exceptions. So the synthesis of a single organic compound sufficed at a blow to break down the chemical barrier which the imagination of the fathers of the science had erected between animate and inanimate nature. Thenceforth the philosophical chemist would regard the plant and animal organisms as chemical laboratories in which conditions are peculiarly favorable for building up complex compounds of a few familiar elements, under the operation of universal chemical laws. The chimera "vital force" could no longer gain recognition in the domain of chemistry.

Two lectures delivered by Louis Pasteur before the Chemical Society of Paris,
on January 20, and February 3, 1860.

FIRST LECTURE

AT the end of the year 1808 Mains discovered that light which was reflected from opaque or transparent bodies possessed new and surprising properties, which distinguished it from the light that proceeded directly from illuminating bodies. Malus called the change which the light suffered by its reflection, polarization. Later the reflection plane itself, i.e., the plane passing through the incident ray and the normal to the reflecting surface, was designated the plane of polarization of the rays. Malus did not, however, limit here his discoveries with regard to polarized light. It had been known for a considerable time that a direct ray of light in passing through
acalcite rhombohedron was divided into two rays of equal intensity. A flame when observed through such a rhombohedron always appeared double and both images were of equal clearness.

Huygens and Newton had earlier found that light which had passed through Iceland spar differed from direct light.

When one or the other of the two images above mentioned is examined through a new rhombohedron, doubling of the image does not always take place ; and when doubling of the image does occur the two new images no longer possess equal intensity.

Light which has passed through a doubly refracting crystal is thus different from natural or direct light.