CULTURE-MEDIA. 75 



sterilization has been effective; if it has not, development of the 

 contaminating bacteria will take place and be visible to the eye. 



It will be impossible to do more than merely mention some 

 of the most important of the other culture-media. 



Loffler's blood-serum consists of one part of bouillon con- 

 taining i per cent, of glucose and three parts of blood-serum. 

 It is sterilized like ordinary blood-serum. It is used largely 

 for the cultivation of the bacillus of diphtheria. 



Blood-serum-agar is a medium made with considerable dif- 

 ficulty, but when made with human blood-serum very valuable 

 for the cultivation of the gonococcus. One part of placental 

 blood-serum, or pleuritic serum, or hydrocele fluid, is mixed 

 with one to two parts of nutrient agar in the fluid condition. 

 It must be divided into tubes before solidification. It should be 

 solidified in a slanting position, and sterilized at 58 C. so as 

 1 not to coagulate the blood-serum. At this temperature it is 

 necessary to sterilize for several successive days (see page 74) 

 and it should be tested in the incubator for sterility. The 

 nutrient agar in this case should contain 2 per cent, of dry agar. 



Another expedient has also been to smear a little blood, drawn from a puncture 

 made by a sterile needle in the carefully cleaned finger, over the surface of a 

 tube of nutrient agar blood-agar used for cultivating the bacillus of influenza. 

 In this case the finger from which the blood is drawn is scrubbed with soap and 

 water, soaked with T ^ ^ corrosive sublimate, and finally washed with alcohol. 

 Small quantities of blood may be drawn from a vein in the ear of a rabbit (see 

 page 103) with a sterile hypodermic syrince, and is quickly divided among three 

 or four tubes of agar, melted in the upper third; slant the tubes while cooling. 

 To make a large amount of blood-agar, bleed a rabbit from the carotid artery 

 into a sterile flask containing pieces of sterile glass tubing; shake the flask con- 

 stantly; divide the defibrinated blood among tubes containing sterile nutrient 

 agar; slant the tubes while cooling. Use one part of blood to about two of agar. 

 Great care must be used not to contaminate the blood as it is drawn, and it is 

 best to test it in the incubator for sterility. The tubes when completed should 

 stand some days before using, so that contaminating bacteria if present may 

 grow in the interval and permit such tubes to be discarded. 



Guarnieri's medium consists of a mixture of gelatin and "agar. 



Eggs in their shells may be used after sterilization by steam, which of course 



