Potatoes 237 



tubes, and sterilized and coagulated like the blood-serum 

 itself. As prepared by Loffler it was soft, semi-gelatinous 

 and semi-transparent, not firm and white ; therefore should 

 be sterilized at low temperatures. Many organisms grow 

 more luxuriantly upon it than upon either plain blood-serum 

 or other culture media. Its especial usefulness is for the 

 cultivation of Bacillus diphtheriae, which grows upon it 

 rapidly and with a characteristic appearance. 



Alkaline Blood=serum. According to Lorrain Smith, a 

 very useful culture medium can be prepared as follows : To 

 each loo c.c. of blood-serum add 1-1.5 c - c - f a IO per cent, 

 solution of sodium hydrate and shake it gently. Put suffi- 

 cient of the mixture into each of a series of test-tubes, and, 

 laying them upon their sides, sterilize like blood-serum, 

 taking care that their contents are not heated too quickly, as 

 then bubbles are apt to form. The result should be a clear, 

 solid medium consisting chiefly of alkali-albumins. It is 

 especially useful for Bacillus diphtheriae. 



Deycke's Alkali=albuminate. One thousand grams of 

 meat are macerated for twenty-four hours with 1200 c.c. of a 

 3 per cent, solution of potassium hydrate. The clear brown 

 fluid is filtered off and pure hydrochloric acid carefully added 

 while a precipitate forms. The precipitated albuminate is 

 collected upon a cloth filter, mixed with a small quantity of 

 liquid, and made distinctly alkaline. To make solutions of 

 definite strength it can be dried, pulverized, and redissolved. 



The most useful formula used by Deycke was a 2.5 per 

 cent, solution of the alkali-albuminate with the addition of 

 i per cent, of peptone, i per cent, of NaCl, and gelatin or 

 agar-agar enough to make it solid. 



Potatoes. Without taking time to review the old method 

 of boiling potatoes, opening them with sterile knives, and 

 protecting them in the moist chamber, or the much more 

 easily conducted method of Esmarch in which the slices 

 of potato are sterilized in the small dishes in which they 

 are afterward kept and used, we will at once pass to what 

 seems the most simple and satisfactory method that of 

 Bolton and Globig.* 



With the aid of a cork -borer or Ravenel potato cutter 

 (Fig. 47) a little smaller in diameter than the test-tube ordi- 

 narily used, a number of cylinders are cut from potatoes. 

 * "The Medical News," vol. i,, 1887, p. 138. 



