802 



SCIENCE 



[N. S. Vol. XXXIX. No. 1013 



as with litmus milk. Treatment witli potassium 

 tellurite was found to have practically no influ- 

 ence on the biochemical reactions of an organism. 



An Improved Technique for Performing the 

 Griiber-Widal Test for Typhoid Fever: F. M. 

 Header, M.D. 



The method herewith described is not new in its 

 elements, but the combination is one which I have 

 not noticed in other laboratories that I have vis- 

 ited or in the literature. We have been using the 

 method in the city laboratory of Syracuse for 

 three months now with considerable satisfaction. 

 A description of the method is herewith offered. 



Apparatus. — There are used the following ma- 

 terials: 1st, a vial with straight sides, 2 cm. long 

 and having a 0.5 cm. lumen. The cork stopper 

 has fixed into the inner surface a lance. (A) 2d, 

 a standard wire loop made from a No. 25 U. S. 

 gauge platinum wire, the lumen of which is 2 mm. 

 in diameter. (B) 3d, a capillary pipette with per- 

 forated nipple, graduated in two places to de- 

 liver the equivalent of 3 and 4 standard loopfuls 

 of serum. (C) 4th, a mixture tray having a 

 dozen or more cells such as is used by artists for 

 mixing paints. (D) 5th, a hanging drop slide. 

 (E) 6th, cover slips. (F) 7th, alboline oil. 8th, 

 sterile salt solution, 9th, a 24-hour bouillon cul- 

 ture of B. typhosus. 



Procedure. — Prepare a control by placing a 

 loopful of salt solution upon a eoverslip. Then 

 mix with it a loopful of the culture of B. typhosus. 

 Place a ring of alboline oil around the depression 

 in the cover glass. Invert the eoverslip over the 

 depression in the slide so that the center of the 

 drop comes over the middle of the depression. 

 Examine under the microscope to see that the cul- 

 ture is active and that the organisms are suffi- 

 ciently numerous. If the preparation is satisfac- 

 tory, the time is noted and it is set aside for one 

 hour. 



Given a sample of blood in vial A. If the vial 

 is about one fourth full of blood, and is then cen- 

 trifugalized, there will be a satisfactory amount 

 of serum present. With the graduated pipette 

 measure 4 loopfuls of salt solution into one of the 

 cells of the mixing tray. Then measure 3 loopfuls 

 of salt solution into another cell of the mixing 

 tray. With the standard loop take one loopful of 

 the serum and mix it with the salt solution first 

 measured out. This makes the dilution of serum 

 1-5. Transfer a loopful of this mixture to the 

 second solution measured out. This makes a dilu- 

 tion of 1-20. Transfer a loopful of this mixture 



to a eoverslip. Add to it a loopful of the culture 

 of Bacillus typhosus. This makes a dilution of 

 1-40. Prepare a hanging-drop slide as above with 

 oil. Invert the eoverslip over the depression and 

 examine under microscope. Note the time and 

 examine one hour later for agglutination. 



The particular point of value in this technique 

 is the use of the capillary pipette. Since there is 

 a perforation in the nipple, the salt solution will 

 rise to the graduations by capillary force, so that 

 an exact amount of diluent can be easily and ac- 

 curately obtained. The liquid can be pushed out 

 into the cell of the diluting tray by covering the 

 perforation with the finger and compressing the 

 bulb. Since the viscosity of serum is greater than 

 that of salt solution, the volume of a loopful of 

 serum will be greater than the loopful of salt so- 

 ution. So that in calibrating the pipette 3 and 4 

 loopfuls of serum should be used instead of salt 

 solution in order that in practise the volumes of 

 diluent and serum will be comparable. The 

 method commends itself for its simplicity, rapid- 

 ity of operation and precision in measurement. 



A Synthetic Medium, for the Determination of 

 Colon Bacilli in Ice Cream: S. Heney Ayeks 

 AND William T. Johnson, Jk. 

 In a study of the bacteria in ice cream we have 

 endeavored to prepare a synthetic medium for the 

 detection of colon bacilli. During the experiments 

 53 diiferent combinations were tried. The most 

 satisfactory medium was made as follows: Agar, 

 1.5 per cent.; asparagin, 0.3 per cent.; sodium di- 

 basic phosphate, 0.1 per cent.; lactose, 1.0 per 

 cent., and 2 per cent, of a saturated solution of 

 litmus. The majority of the bacteria in ice cream 

 did not grow on this medium, while colon bacilli 

 showed quite characteristic acid colonies which 

 with a little practise could be readily detected. 

 The colon count on litmus lactose asparagin agar 

 was compared with the estimated number from 

 lactose bile tubes in 43 samples of ice cream. In 

 41 of the 43 samples the number determined on 

 the plates was higher than the estimated number 

 from the bile tubes. 



Suspected colon colonies on the asparagin plates 

 from 19 samples were picked off and inoculated 

 into lactose broth fermentation tubes. From ten 

 plates all the suspected colonies, or 100 per cent., 

 proved to be gas formers. Among the other nine 

 plates the percentages ranged from 87.17 per cent, 

 to 98.01 per cent. This shows that it is possible 

 to detect quite accurately any colonies of gas- 

 forming bacteria on litmus lactose asparagin agar. 



