342 



BULLETIN No. 161 



[November, 



each flower pot placed in a gallon glass jar containing water and 

 immersed about three inches, so that the level of the emulsion of 

 tubercle bacilli on the inside was the same as the level of the water 

 on the outside. The water in the glass jars around the outside of 

 the flower pots was kept continually running. While this procedure 

 does not give the same condition as water running directly into the 

 emulsion of bacteria, it allows to some extent the circulation of the 

 water inside the porous flower pot with running water on the out- 

 side of these vessels. Another part of the emulsion of bovine tu- 

 bercle bacilli was kept in a cotton-stoppered glass bottle. This 

 bottle was partly immersed in one of the glass jars of running 

 water. The water could in no way circulate in this bottle, but it 

 was kept at approximately the same temperature as the emulsions in 

 the flower pots. 



The samples were kept in the laboratory until April 15, 1911, 

 250 days after the emulsions were first made. It was then found 

 neither convenient nor desirable to keep them there longer. A 

 pool was prepared in the courtyard of the Agricultural Building, 

 to which they were transferred. The pool ^as made by sinking a 

 large tile three feet in diameter and filling in the bottom with 

 concrete. Constantly running water was maintained to a depth of 

 twenty inches the year round. It did not freeze any time during 

 the winter of 1911-12. A shelf of slate was placed four inches 

 under the surface of the w T ater on which the vessels containing the 

 tubercle bacilli were set. The pool was screened against flies and 

 other insects. (See Figs, i and 2.) 



FIG. 2. THE POOL/ SCREENED AGAINST 



