10 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



and it is an advantage to place a shallow layer of a solution of 

 perchloride of mercury (or other non-volatile antiseptic) in the 

 bottom of each jar to prevent the medium from drying up. It is 

 scarcely necessary to add that not the smallest trace of the lotion 

 should be allowed to come into contact with the cotton-wool 

 plug of the tubes, Or the medium may be kept from drying 

 up by covering the tubes with indiarubber caps sold for the 

 purpose. 



Messrs. Burroughs and Wellcome now manufacture certain 

 culture media in tabloid form. To prepare broth or agar-agar it 

 is only necessary to place a suitable tabloid in a sterilized test- 

 tube containing 5 c.c. of water. The tube is now plugged 

 with cotton -woo! and boiled until the tabloid is completely 

 dissolved. This will be hastened if it is crushed or powdered 

 previously. If the water used is free from spores, as a rule the 

 culture medium is sterile, but where an autoclave is at hand it 

 should be used. These tabloids will be found very convenient for 

 practitioners who are not engaged in regular bacteriological 

 work. 



Broth is very easily made, and, as it is the foundation of many 

 other media, the practitioner is strongly advised to prepare it for 

 himself. 



Requisites. — i. Liebig's Extract of Meat. 



2. Peptone. 



3. Common salt. 



4. A dilute solution of sodium carbonate — about i per cent., 

 but the exact strength does not matter. 



5. A large flask, a stirring-rod, and a large glass funnel. 



6. Test-tubes and cotton-wool plugs. The exact size of the 

 tubes is unimportant, but 6 inches by | inch is convenient. The 

 plugs are best prepared from wool which has been previously 

 sterilized by dry heat, and should be fairly firm. The tube, 

 with the plug in situ, must be sterilized by dry heat ready 

 for use. 



7. Litmus-paper. 



Method. — Take i litre of tap-water in the flask, and add 

 5 grammes of Liebig's Extract, 10 grammes of peptone, and 

 5 grammes of common salt, and boil until all are dissolved. Test 

 the reaction by withdrawing a drop of the fluid on the stirring-rod 

 and applying it to a piece of litmus-paper. You will probably 

 find that it is slightly acid. Now add some of the solution of 



