His work in cell culture began in about 1910 or 11 and it was about that time that he initiated this culture from a chick heart... embryonic chick heart cells and he was... he believed, strangely enough... and because this was a very serious problem in cell culture until the antibiotic era, the problem being the frequent contamination of cell culture with bacteria from the atmosphere. As you worked on the cultures, you had to open and close vessels, bottles, and frequently bacteria would fall in, contaminate the culture and your experiment was finished, so major efforts were made, prior to the antibiotic era, to prevent this from happening. All kinds of procedures were conducted. Carrel felt that everything had to be painted black in order to reduce the likelihood of contamination. Not only the rooms themselves, floors, ceilings and walls, but also the workers themselves, who were gowned from head to foot in black attire looking like Ku Klux Klan figures roaming about this large laboratory facility.