Abstract
The activity of human milk for the growth of Lactobacillus bifidus var. Penn was compared with that of other species. The average relative activity was highest for human colostrum, closely followed by rat colostrum, then by human milk, rat milk, and cow's colostrum. The milk of ruminants (cow, ewe, goat) showed only very slight activity. Somewhat higher activity was found in the milk of cat, monkey, dog, donkey, rabbit, mare, and sow.
The bifidus growth factor has been demonstrated in high concentration in various secretions in man, such as saliva, semen, amniotic fluid, meconium, and tears. Hog gastric mucin which has a high blood-group titer has also shown a high titer for bifidus factor, while other nitrogencontaining polysaccharides were free or almost free of bifidus factor.
Ammonium salts and N-acetylglucosamine as well as N-acetylgalactosamine, especially the ammonium salts, in high concentration, were active, probably as precursors of the growth factor.
