10 APPARATUS. 



of motility or agglutination which does not dry out for hours, and 

 is easier to focus upon than the concave slide hanging-drop preparation. 

 The fermentation tube with a bulb and closed arm is expensive, 

 difficult to clean and is easily broken. As a substitute in the study 

 of gas production and in water bacteriology, the Durham tube is to be 

 recommended. Into a test-tube, about i x 7 in., we introduce the 

 special sugar media, then drop down a small test-tube (1/2 x 3 in.) 

 with its open end downward. Insert the plug of the large tube and 

 sterilize. During sterilization the fluid enters the mouth of the smaller 



FIG. 4. Blood serum coagulating apparatus. 



tube and fills it, and when the medium is subsequently inoculated, if gas 

 forms, it appears in the upper part of the closed end of the smaller tube. 

 For inspissating blood serum slants a regular inspissator is desirable. 

 This is nothing more than a double-walled vessel, the space between 

 the walls being filled with water. As a substitute one may take the 

 common rice cooker (double boiler). Fill the outer part with water; 

 and in the inner compartment pack the serum tubes properly slanted 

 on a piece of wood or a wedge-shape layer of cotton. Place a weight 

 on the cover of the inner compartment to sink it into the surrounding 

 water, and allow to boil for one or two hours. This same apparatus 

 may be used for their sterilization on two subsequent days, but it is 

 better to sterilize in the autoclave or Arnold. As regards a working 

 desk, it will be found convenient to have an arrangement similar to the 

 ordinary flat-top desk, w r ith a tier of drawers on each side. A block 



