BLOOD SERUM 25 



solution. Transfer to a filter. Wash out the dish with alcohol and add this to 

 the filter. Wash the precipitate on the filter with alcohol. Dissolve the pure 

 coloring matter remaining on the filter in warm distilled water and dilute to 500 c.c. 

 Azolitmin solution prepared in this way is more sensitive than ordinary litmus 

 solution. 



Azolitmin in powder can be purchased from dealers in chemicals. 



POTATO SLANTS. 



Take Irish potatoes and scrub throughly with a stiff brush. Then pare off 

 generously all the outer portion. From the white interior cut out cylinders with a 

 cork borer. These cylinders should be of 1/2 to 3/4 of an inch in diameter. Di- 

 vide a cylinder by a diagonal cut. This gives a plug with a flat base, the other 

 extremity being a slant. These potato plugs should be left in running water over 

 night or washed with frequent changes of water. This prevents the blackening of 

 the plug. Into a i-in. test-tube drop a pledget of absorbent cotton well moistened 

 with water. Then drop in the potato plug, base downward. Sterilize in the auto- 

 clave at 15 pounds for fifteen to twenty minutes, to insure sterility. 



For glycerine potato, soak the plugs in 6% glycerine solution for about one hour. 

 Then drop a pledget of absorbent cotton moistened with the same glycerine 

 solution into the test-tubes and follow it with the potato plug. Sterilize in the 

 autoclave. 



BLOOD-SERUM. 



The blood of cattle should be collected in large pans or pails at the abattoir. 

 This vessel of blood should then be kept in the cold-storage room and the next 

 morning the more or less clear serum will have been squeezed out from the clot. 

 Collect this serum and keep in the ice chest for future use. If to be kept for along 

 time, it is advisable to add about 2% of chloroform to the serum in tightly corked 

 flasks. This will not only keep the serum, but will eventually sterilize it. 



To make Loffler's serum, take one part of glucose bouillon and three parts of 

 blood-serum. Mix, tube, and coagulate the albumin in the inspissator or rice cooker, 

 giving the tubes a proper slant before heating. Sterilize the following day in the 

 autoclave as previously directed (7 Ibs.) or in the Arnold on three successive days. 



A SUBSTITUTE FOR ORDINARY BLOOD-SERUM. 



Add from 10 to 15 c.c. of i% glucose bouillon to the white and yolk of one egg, 

 make a smooth mixture in a mortar and tube. Inspissate and sterilize as for ordin- 

 ary serum slants. The morphology of the diphtheria bacilli and the luxuriance of 

 growth is similar to that of cultures on Loffler's serum. 



When this medium is to be used for culturing tubercle bacilli add about i c.c. 

 of glycerine bouillon to each tube before final sterilization in the autoclave. The 

 cotton plugs should be paraffined to prevent drying of the slants in the incubator. 

 This medium seems to answer as a substitute for Dorset's egg medium. While 

 glycerine bouillon favors growth of human tuberculosis, it is not so satisfactory for 



