STOOD ART'S MEDIA. 493 



The other portion of 500 c.c. of meat extract is also 

 titrated and an excess of 10 c.c. of N NaOH per liter is ad- 

 ded. The liquid is weighed; then boiled and filtered. To the 

 clear bouillon, thus obtained, 5 g. of finely cut agar are 

 added. The liquid is gently boiled till the agar has com- 

 pletely dissolved, when it is weighed. The loss in weight 

 is compensated by the addition of a corresponding amount 

 of distilled water. An equal volume of the 10 per cent, 

 gelatin, prepared as above, is then added and the mixture 

 is sedimented, as in the case of agar (p. 236), at 50 for 1-2 

 hours. It is then filtered through the absorbent cotton 

 filter (p. 237), and, if desired, it can then be passed through 

 a filter paper. 



The preparation of this medium can be simplified by heating- the 

 liter of meat extract till the soluble proteins coagulate. To the 

 clear filtrate 5 g. of agar are then added and the liquid is boiled till this 

 has dissolved. 50 g. of gelatin are then dissolved in this agar solution- 

 and the liquid is titrated. To the amount of normal alkali necessary 

 to neutralize the medium an excess of 10 c.c. per liter is added to im- 

 part the desired alkalinity. The liquid is then heated in a water- 

 bath for about 30 minutes, allowed to sediment at 50, and finally 

 is filtered as above. 



It is evident that Stoddart's medium is a gelatin-agar 

 which contains: 



Gelatin, 5 per cent. Agar, 0.5 per cent. 



Pepton, 1.0 per cent. Salt, 0.5 per cent. 



The medium is filled into large test-tubes, in portions 

 of about 10 c.c., and sterilized by exposure to steam for 15 

 minutes on each of three successive days. 



The method of using the medium is as follows: It is poured out 

 into wide (7 cm.) Esmarch dishes, steamed and allowed to solidify in a 

 horizontal position. The organism to be tested is touched, by means 

 of a platinum wire, to the center of the surface of the medium. The 

 dishes thus prepared are placed over some water in a moist chamber. 

 The latter is placed in a horizontal position, in the incubator at 35. Ins, 

 about 18 hours, the Eberth (and Sanarelli) bacilli will spread over the- 



