Attenuation

(at-ten-u-a' 'shun). A thinning, narrowing, or reduction of the strength or size of a substance. A. of Microbes, weakening the pathogenic virulence of microbes by succe ive cultures and other methods, so that they may be used as a vaccine to confer immunity from future attacks of the disease. A., Sanders on's Method of, by pa ing the virus through the system of another animal (e.g., the guinea-pig, in anthrax), so that it becomes modified in virulency. To us saint and Chauveau have shown that heat is a valuable means of attenuation; oxygen, chemical reagents, exposure to sunlight, etc., have also been used.