CUL TIVA TION OF BA CTEBIA. 485 



two parts. The pieces are then placed in test-tubes with a little dry 

 cotton at the bottom ( to absorb the water of condensation) and steril- 

 ized several times in the steam chamber. 



14. Blood -serum. — Blood, obtained from slaughtered animals 

 under proper precautions, is allowed to stand in a refrigerator in 

 well-cleaned glass cylinders for twenty-four hours. Then the serum is 

 removed with large sterile pipets. It is then placed in flasks with the 

 addition of 1% of chloroform and allowed to stand several weeks, 

 being occasionally shaken. Before using, the tubes, into which the 

 serum has been filled, are placed in the incubator for a few days to 

 insure complete evaporation of the chloroform. It may be used as a 

 fluid or after being solidified at 65°. 



15. Loffler's serum mixture for diphtheria bacilli : Three parts of 

 beef- or sheep-serum are mixed with 1 part of veal bouillon which 

 contains 1% grape-sugar, 1% peptone, and 0.5% NaCl. 



16. Ascitic Fluid, Fluid from Ovarian Cysts. — The fluid obtained 

 by puncture has added to it a little chloroform (30-50 gm. to liter) and 

 is stored in a dark place for several weeks or months, being frequently 

 shaken. If the fluid is clear like water it is drawn into a sterile pipet 

 and filled into test-tubes. The tubes are placed in a water-bath for 

 half an hour at 30°-35° to drive off the chloroform. 



Glycerin-ascites-agar is prepared by mixing equal parts of the 

 above fluid and of ~2% nutrient agar which has been liquefied, cooled 

 down to 40°, and which contains 5% glycerin. This medium re- 

 places blood -serum in most cases, and upon it we have observed a very 

 good growth of the organisms of gonorrhea, pneumonia, tuberculosis, 

 whooping-cough, and diphtheria, and of streptococci and Bact. duplex 

 (Morax's diplobacillus). 



17. Silicic acid nutrient medium is very different from the other 

 media. It was first devised by Kiihne, and has been modified by 

 various authors. Gelatinous silicic acid, which is merely mixed with 

 certain salts, is an important nutrient medium for some organisms 

 (for example, the nitrate producers) because of the lack of organic 

 nutrient substances. For the rather complicated preparation consult 

 Stutzer and Burri (C. B. L. 1, 722). 



18. As a substitute, Beijerinck has recommended a water agar, pre- 

 pared by extracting for a long time with distilled water, from which 

 the nutrient substances are removed by decomposition and diffusion 

 and to which the salts may be added (C. B. xix, 258). 



19. Cerebral Nutrient Medium (v. Hibler). — Human brain from 

 fresh cadavers is cut up finely with a chopping machine, placed in 

 small flasks, and stirred up with enough distilled water to form a semi- 

 fluid infusion. The masses are then sterilized. Before using, the 

 nutrient medium is again boiled for half an hour. 



20. Nutrient Medium for Differentiation of Species of Actino- 

 myces. — The following is recommended by Gasperini: 



Wheat flour 150 



Water 1000 



Magnes. sulph 0.5 



Potass, nitrate 1.0 



Grape-sugar 15.0 



