GROWTH OF BACTERIA IN THE ANIMAL BODY 53 
A neutral or feebly alkaline reaction is best adapted to the de^'elop- 
ment of the vast majority of bacteria; a few types develop best in a 
medium which is distinctly acid— the aciduric bacteria. ^ Mineral 
acids are germicidal; organic acids may be utilized by bacteria for 
foods.- 
O. GROWTH OF BACTERIA IN THE ANIMAL BODY. 
The vast majority of bacteria do not grow in the tissues of the body, 
although a small number of organisms, the parasitic bacteria, live 
habitually on the surface of the body or on mucous membranes, usually 
without producing noticeable effects. A small, formidable group of 
bacteria, the progressively pathogenic bacteria, actually invade the 
tissues; they may produce within the host inhibition of function or 
anatomical changes incompatible with health. 
» Kendall: Jour. Med. Research, 1910, 22, 153. 
- For a discussion of Bacteria and Vitamins, see The Newer Knowledge of Nutrition, 
McCollum and Simmonds, 3d ed., 1925, pp. 268, 270, 301. 
