606 irUMMARY OF CURRENT RESEARCHES RELATING TO 



alkaline salts of milk produce formic acid at the expense of the lactose 

 when milk is heated to 130° C. The differentiation of organisms by 

 means of sugar media is rendered difficult by this fact, a slight degree 

 of fermentation being simulated. Bourdet recommends in practice that 

 (1) broth media should be sterilized by filtration after the addition of 

 the pepton and the alkali ; (2) separate sterilization of the sugars 

 required for the media, and their aseptic admixture with the broth 

 media ; (3) the separate sterilization of the litmus solution. 



Culture of Diphtheria Bacilli in Veillon's Tubes.*— L. Martin 

 and G. Loiseau recommend the following technique for the differen- 

 tiation of true diphtheria bacilli from pseudo-diphtheria bacilli. It is 

 based on the fact that Bacillus diphtherise is a facultative anaerobe, while 

 the other organisms are strict aerobes. 



Tlie medium employed is prepared as follows: 250 grm. of minced 

 veal added to 500 c.cm. water are mixed with equal parts of " bouillon 

 de panse (pepton martin)." To each litre of this mixture is added : 

 Agar s grm. glucose 15 grm., and potassium nitrate 2 grm. Dis- 

 solve and add the white of one egg, heat to 115° C. for half-an-hour, 

 filter, tube, and sterilize for half-an-hour at 100° C, and, during the 

 three days following, for half-an-hour at 115° C. 



A pure colony of the organism to be investigated is emulsified in a 

 tube of 10 c.cm". broth. The organisms are then well distributed by 

 shaking. Add 1 c.cm. of this emulsion to a tube of the glucose agar 

 medium (previously boiled and cooled rapidly to 50° C.) and mix care- 

 fully. Incubate when solid. True diphtheria bacilli are easily identified, 

 as the colonies are evenly distrilnUed throughout the tube without 

 prominence in the aerobic zone, while colonies of B. Hoffmann and 

 other diphtheroids only grow in the superficial zone, and not in the 

 strictly anaerobic portion of the medium ; moreover, the growth is less 

 rapid than with the diphtheria bacillus, and is not generally visible for 

 at least twenty-four hours. 



Digested and Diluted Serum as a Substitute for Broth. t — A. 

 Distaso suggests the use of the following medium in the place of 

 ordinary broth in bacteriological work : (1) One volume of sheep or 

 ox serum is mixed with one volume of tap-water, and boiled till it 

 becomes milky. (2) A pig's pancreas is minced and extracted with 

 400 c.cm. of distilled water in the presence of chloroform for twenty-four 

 hours ; and (3) a piece of the upper part of the small intestine is 

 extracted in the same way, in order to activate the pancreatic extract. 

 To one litre of (1) is added 100 c.cm. of (2) and 10 c.cm. of (3), and 

 digested at 60° C. for the night. Next morning the flask contains an 

 amber-coloured liquid with fine flocculi floating in it. Filtered through 

 Chardin paper, the amber-coloured liquid passes through, and the flocculi 

 remain in the filter. The liquid is collected and sterilized at 120° C. 

 for fifteen minutes, then tubed and re-sterilized. In this medium the 



* C.E. Soc. Biol. Paris, Ixxix. (1916) pp. 677-80. 

 t Brit. Med. Journ., 1916, pp. 555-6. 



