BACTERIOLOGICAL TECHNIC 



sterile jar or flask, closed with cotton plug. Place on ice for twenty-four 

 to forty-eight hours, during which time coagulation has taken place; the 

 serum may then be siphoned off. The proper sterilization of Loeffler's 

 serum requires care. After the bouillon and serum 

 are mixed, pour into test-tubes and coagulate in a 

 Koch serum coagulator at a temperature of 80 C. 

 Any form of sterilizer may, however, be used. The 

 essentials are that the temperature should be raised 

 very gradually and must be kept below the boiling- 

 point, .and the tubes should be slanted at a degree 

 which will bring the medium close to the cotton plug, 

 making what are commonly called tube slants. After 

 the medium is coagulated in the tubes it is sterilized 

 fractionally on three successive days (one hour each 

 day) at a temperature of 80 C. These tube slants 

 are now ready for the physician. 



To prevent evaporation of the medium in the 

 test-tubes, cover the cotton plug and upper end of 

 tube with tin foil fastened with thread, and dip into 

 melted paraffin several times. Tubes thus sealed can 

 be kept for a year or more without any considerable 

 shrinking of the medium. Dip the tin foil in a i : 2000 nosis O f diphtheria. 

 corrosive sublimate solution before capping on tubes, should be long 



A simpler way is to use rubber caps which are enough to have the 



11 j -C.L .1.1- j r it. i u entire length of swab 



especially made to fit over the end of the test-tube i ns ide, no t project- 



and the cotton plug. These rubber caps must be 



sterilized before applying them, for which purpose 



the 1-2000 corrosive sublimate solution will be found satisfactory. 



Rubber stoppers may also be used but they are more expensive and 



inferior to the rubber cap or the tin foil with coat of paraffin. 



C. Liquid Blood Serum. Obtained as for Loeffler's serum. Sterilize 

 fractionally at a temperature of from 56 to 58 C. for one hour on each 

 of six days. The serum will be liquid and clear. 



D. Milk. Secure fresh milk directly from cow, or, if in cities, demand 

 certified milk. Keep on ice, in a covered jar, for twenty-four hours. 

 Siphon off the middle portion, rejecting cream and sediment. Sterilize 

 like Loeffler's blood serum. Litmus milk is prepared by adding i per cent, 

 of azolitmin before sterilizing. This indicator will show whether or not 

 acids are formed by the microbes which may be cultivated in the milk. 

 Only pure milk will answer the purpose. Milk to which preservatives 

 (formaldehyd, salicylic acid, borax, boric acid) have been added must 

 not be used. 



FIG. 19. Cul- 

 ture tube and swab 

 tube used by phy- 

 sicians in the diag- 



ing as shown in the 

 figure. (Williams.) 



