12 



APPARATUS 



Into a test-tube, about 1X7 inches, we introduce the special sugar media, then 

 drop down a -small test-tube (KX3 inches) with its open end downward. Insert 

 the plug of the large tube and sterilize. During sterilization the fluid enters the 

 mouth of the smaller tube and fills it, and when the medium is subsequently inocu- 

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



FIG. 4. Blood serum coagulating apparatus. 



Inspissators. For inspissating blood-serum slants a regular inspissa- 

 tor 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-shaped 

 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 auto- 

 clave or Arnold. The rice cooker is of the 

 greatest use in preparing culture media. For 

 this purpose the outer compartment is filled 

 with calcium chloride solution or a 25% solu- 

 tion of common salt, so that the tempera- 

 ture of the contents of the inner receptacle may be raised to the boiling point. 

 Of course media may be prepared in an ordinary sauce-pan but there is great 

 danger of scorching media prepared in this way. Special vessels with two bottoms, 

 between which is an air space, are now on the market and have an advantage 

 over the double boiler (rice cooker). 



Ebony Finish. As regards a working desk, it will be found convenient to have an 

 arrangement similar to the ordinary flat-top desk, with a tier of drawers on each side. 



FIG. 5. Rice cooker. 



