Potatoes 197 



and ruin its surface. The autoclave temperature unfortunately 

 makes the preparation very firm and hard, considerable fluid being 

 pressed out of it. 



It is said that considerable advantage is secured from the addition 

 of neutrose to blood-serum, which prevents its coagulating when 

 heated. It can then be sterilized like bouillon and can subsequently 

 be solidified, when desired, by the addition of some agar-agar. 



Fresh blood-serum can be kept on hand in the laboratory, in 

 sterile bottles, by adding an excess of chloroform. In the process 

 of coagulation and sterilization the chloroform is evaporated; the 

 serum is unchanged by its presence. 



Loffler's Blood-senim Mixture, which seems rather better for the 

 cultivation of some species than the blood-serum itself, consists of 

 I part of a beef-infusion bouillon containing i per cent, of glucose 

 and 3 parts of liquid blood-serum. After being well mixed the fluid 

 is distributed in tubes, and sterilized and coagulated like the blood- 

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

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

 ized 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 diphtherise, 

 which grows 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 100 cc. of blood-serum add i-i.S 

 cc. of a 10 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 

 diphtherise. 



Deycke's Alkali-albuminate. — One thousand grams of meat are macerated for 

 twenty-four hours with 1 200 cc. of a 3 per cent, solution of potassium hydrate. 

 The dear 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 

 boiUng 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 a little 

 smaller in diameter than the test-tube ordinarily used, a number 

 of cyUnders are cut from potatoes. Rather large potatoes should 



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



