The Bacillus of Long Life / A Manual of the Preparation and Souring of Milk for Dietary Purposes, Together with an Historical Account of the Use of Fermented Milks, from the Earliest Times to the Present Day, and Their Wonderful Effect in the Prolonging of Human Existence

by Loudon M. Douglas

Spore forming bacillus

Staphylococcus pyogenes albus

Fig. 42—Photograph of Test Tubes of Sterile Milk, inoculated with a tablet preparation said to contain pure cultures. The darker liquefied portion of the tube-contents is due to digestion of the curd by proteolytic bacteria, thus indicating impure culture. Pure cultures of lactic acid bacteria coagulate the milk uniformly, but do not produce any subsequent change in the appearance of the culture, even after several months.

Fig. 43— Photograph of Test Tubes of Sterile Milk, each tube having been inoculated with a tablet of a preparation said to contain pure cultures. Here, again, there is evident peptonisation of the curd, thus indicating infection by proteolytic ferments. Cultures from these tubes demonstrated the presence of a foreign organism. Microscopical examination failed to disclose the presence of Basillus Bulgaricus.

Fig. 44—Photograph of Test Tubes of Sterile Milk, inoculated with a tablet of "Lactobacilline." In contra-distinction to those shown in Figs. 42 and 43, these tubes exhibit homogeneous curdling of the milk without any subsequent digestion or peptonisation of the coagulum. This is indicative of the purity of the culture.