140 THE AMERICAN MONTHLY [Aug 



tion of oxygen by alkaline pyrogallol and its removal by 

 the use of an air-pump. If milk, boiled and sterilized? 

 be mixed with sewage, placed under ansBrobic conditions, 

 and examined after twenty-four hours' incubation, it will 

 be found clear in one part, while the top and bottom por- 

 tions of the vessel will be occupied by a coagulum. 

 The liquid literally teems with anaerobic bacteria. 



Bacteria which cause phosphorescence on old, rotton 

 wood, and the bones of dead fish next received attention. 

 In such cases the bacteria either themselves become 

 luminous or else produce a luminous secretion. A me- 

 dium composed of broth with small proportions of 

 sodium chloride and asparagin favors the multiplication 

 of these luminous bacteria in the course of 48 hours in- 

 cubation. An exquisite photograph was shown of a 

 flask filled with a fluid charged with such bacteria ; the 

 plate and flask were left in the dark for several hours 

 and a strikingly beautiful picture was produced. Slides 

 were then placed in the lantern, showing many specific 

 forms of bacteria, including those of anthrax, tubercu- 

 losis, influenza, as well as those which convert urea into 

 ammonium carbonate, nitrites into nitrates, and give rise 

 to other well-known and important changes in nature. 

 It was shown how useful are the bacteria which invade 

 the roots of leguminous plants in enabling a plant to 

 absorb its supply of nitrogen direct from the atmosphere. 

 The question of the choice of suitable dyes was then dis- 

 cussed, and the various aniline dyes, e. g., methyl blue 

 and gentian violet passed in review. A slide was exhib- 

 ted of the bacteria cultivated from the expectoration of a 

 person suffering from tuberculosis. The culture had 

 been stained with fuchsin and then treated with nitric 

 acid, which discharges the color from all bacteria except 

 the tubercular bacillus. The discovery of a method of 

 isolating this dreadful scourge was made in 1882 by 

 Koch, and enabled him to prove conclusively that tabes 



