Alfred Fischer,1 professor of botany in Leipzig, has studied the action of different kinds of serums and other fluids on the bacterial cell, in order to throw more light on the nature of the bactericidal effects of serums. Heretofore the theory of the bactericidal action of serums almost universally adopted is Buchner's alexin theory, which explains the bacterial destruction as caused by digestive ferments. In fact, alexin—or protective body—is held to be a proteolytic enzyme.
Baumgarten and his pupils, however, have rather persistently opposed Buchner's theory, claiming that much of the bactericidal action is due simply to disturbances of nutrition, and of osmosis in the bacterial cells placed in serums of varying composition outside of the body. Alfred Fischer also shows that the sensitiveness of bacterial cells to osmotic disturbances induced by sudden changes in the concentration of the fluids has not been taken into proper account in the