158 BIOLOGY AND TECHNIQUE 



an aqueous litmus solution until the proper color, a deep transparent blue, 

 is obtained, rather than rigid adherence to any quantitative directions). With 

 many batches of serum, it will be found that the addition of two or three 

 times its bulk of distilled water is not a sufficient dilution to prevent 

 coagulation. It will often be found necessary to add four or five volumes 

 of distilled water to one volume of serum. One per cent of the Andrade 

 indicator may be substituted for the litmus. Add to the various fractions 

 of the medium thus made one per cent respectively of the sugars which are 

 to be used for the tests. 



For the preparation of inulin medium, made in this way for pneumococcus- 

 streptococcus differentiation, it is necessary to sterilize the inulin dissolved 

 in the water to be added to the serum in an autoclave at high temperature 

 (15 pounds for 15 minutes) in order to kill spores before mixing- with the 

 serum. The serum-water media are sterilized by the fractional method at 

 100 C., at which temperature they remain fluid. 



Chocolate Media (Park and Williams). It has recently been observed 

 that for the -cultivation of organisms like the influenza bacillus, meningococcus, 

 and a number of other of the more delicately growing bacteria, an excellent 

 medium can be made up in the following way: Agar or broth are made 

 up as usual, and to them added defibrinated rabbit, beef, horse or human blood 

 in proportions of from 5 per cent to .10 per cent by volume. This mixture 

 is then heated gradually up to about 75, until the blood begins to coagulate 

 and assume a dark brown chocolate like color. The broth or agar can first 

 be adjusted to the desired reaction, but it is likely that any excess alkali 

 or acidity is corrected by the proteins which are added. The medium can 

 be tubed, or, in the case of agar, plated or slanted, as it is, after distribution 

 of the blood throughout the medium by shaking. 



In the case of broth the medium can be filtered through paper while 

 hot, and sterilized subsequently by filtration and fractional heating. Such 

 filtrate consists of a clear brownish fluid on which influenza bacilli and other 

 organisms grow with enormous speed. The speed with which influenza bacilli 

 grow on this medium, and its almost complete freedom of hemoglobin, but 

 very much increased cholestrin and other lipoid contents, have lead us to 

 believe that it is not the hemoglobin particularly which is needed for influenza 

 bacillus cultivation. 



SPECIAL MEDIA FOR COLON TYPHOID DIFFERENTIATION 



Conradi-Drigalski Medium.- Original directions. 



(a) Three pounds of meat are infused in two liters of water for twelve 

 hours or more. Strain, boil for one hour and add 20 gms. Witte's pepton, 

 20 gms. of nutrose, 10 gins, of NaCl ; boil one hour and filter. Add 60 gms. 



(Jonrvdi- VripateM, Zeit, f, Hyg. z xxxix, 1902, 



