POTATO Ml.DIA. 



successive days or in the autoclave at 8-10 pounds' pressure for ten 

 minutes. The tubes should be cooled as quickly as possible in cold 

 water after taking out of the sterilizer. 



LITMUS MILK. 



Milk for media should be as fresh as possible. It should then be 

 put in a 1000 c.c. Erlenmeyer flask, sterilized for fifteen minutes in the 

 Arnold and set over night in the refrigerator. The next 

 morning the milk beneath the cream should be siphoned 

 off. The short arm of the siphon should not reach the 

 bottom of the flask so as to avoid the sediment. Add 

 sufficient tincture of litmus to this milk to give a decided 

 lilac tinge; tube and sterilize in the Arnold on three suc- 

 cessive days. 



POTATO SLANTS. 



Take Irish potatoes and scrub thoroughly 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. Divide 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, FlG 

 base downward. Sterilize in the autoclave at 15 pounds Potato in 

 for fifteen to twenty minutes, to insure sterility. 



For glycerin potato, soak the plugs in 6% glycerin 

 solution for about one hour. Then drop in a pledget of absorbent 

 cotton moistened with the same glycerin 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 blocd should then be kept in the cold-storage 



