218 



SCIENCE. 



[X. S. Vol. XXIII. No. 580. 



would contain approximately the same 

 number of units as the curative dose of 

 antidiphtheric serum, as recommended by 

 the U. S. Pharmacopoeia. 



A Method of Isolating the Pneumococcus 

 in Mixed Cultures, Such as Throat Cul- 

 tures: GusTAv F. RuEDiGBR, Memorial 

 Institute of Infectious Diseases, Chicago. 

 Starting with Hiss's demonstration that 

 pneumococci ferment inulin while strepto- 

 cocci fail to ferment it, Ruediger has pre- 

 pared a blue litmus inulin-agar medium in 

 which the pneumococci form red colonies. 

 This medium is composed of sugar-free 

 agar with the addition of litmus and inulin 

 and is prepared as follows : 



(a) Peptone (Witte), 10; agar, 15; 

 sugar-free beef broth (neutral), 1,000. 

 Dissolve by boiling one hour, adding water 

 from time to time. Heat in the autoclave 

 for fifteen to twenty minutes (to prevent 

 subsequent precipitation while sterilizing), 

 clarify with egg and filter through cotton, 

 making the volume up to 800 c.c. with dis- 

 tilled water. 



(&) Dissolve 15 grams of pi;re inulin 

 in 200 c.c. of boiling distilled water and 

 add this solution to (a). Now add 20 c.c. 

 of a five-per-cent. solution of litmus 

 (Merck's highest purity) and tube, putting 

 7 to 8 c.c. of medium into each tube. 

 Sterilize in the autoclave under ten pounds 

 of pressure for fifteen minutes. As some 

 pneumococci do not grow well in this 

 medium it is necessary to add 1 c.c. of 

 heated ascites fluid or serum to each tube 

 of melted agar (which has been cooled to 

 45°) immediately before using. In this 

 mixture the pneumococci grow well and 

 form red colonies in twenty-four to sev- 

 enty-two hoiars. 



Ruediger has shown further that pneu- 

 mococci are practically the only mouth 

 bacteria that ferment inulin. It is not 

 fermented by streptococci (Hiss), staphylo- 



cocci, pseudodiphtheria bacilli. Micrococcus 

 catarrhalis, Micrococcus tetragenus and 

 Bacillus mucosus. Among ten cultures of 

 diphtheria bacilli was found one which 

 fermented inulin. Twenty-two cultures 

 which were made from red colonies in 

 plates that had been inoculated with ma- 

 terial from throats of pneumonia and scar- 

 let fever patients were studied in detail. 

 All are Gram-positive cocci which grow 

 chiefly in pairs on blood agar slants, but 

 some also form chains in liquid media. All 

 ferment inulin and all but four form green 

 colonies in blood agar plates. Capsules 

 could be demonstrated on more than half 

 of the cultures. 



The full paper will be published in the^ 

 Journal of Infectious Diseases, January, 

 1906. 



Observations upon the Phagocytic Power 

 of the Blood of Normal Human Beings: 

 Joseph McFarland and Edwaed M. 

 L'Engle, Philadelphia. 

 The blood of fifteen presumably normal 

 individuals was examined by the method 

 devised by Leichman and modified by 

 Wright and Douglas and by ourselves. 

 Twenty-four-hour cultures of Staphylococ- 

 cus pyogenes aureus were used in all the 

 experiments. We found that the phago- 

 cytic index varied from 23.125 to 4.35. In 

 two cases in which the counts were repeated 

 at intervals of five days there was a re- 

 markable uniformity in one case and a dis- 

 tinct variation in the other. The experi- 

 ments were all performed between the 

 hours of three and five in the afternoon. 

 All of our blood preparations were stained 

 by Marino's method, which we have found 

 the most satisfactory for our purposes. 

 We also found that the number of bacteria 

 taken up by the leucocytes varies with 

 great regularity according to the strength 

 of the bacterial suspension used. Hence, 

 we have endeavored to use a uniform sus- 



