1434 



Journal of Applied Microscopy 



MEDICAL NOTES. 



Robin, A. A Contribution to the Techinic of 

 the Widal Test. Phila. Med. Jour. 7: ii. 



Four problems present themselves to 

 the bacteriologist who attempts to per- 

 form the Widal test in the diagnosis of typhoid fever, viz. : 1. The dilution. 



2. The best way of obtaining a motile culture free from " natural " clumps. 



3. The differentiation between a true and a pseudo-reaction. 4. The time limit. 



To these problems Dr. Robin offers solutions which in his expe- 

 rience have proved most practical and satisfactory. 



1. Accurate dilutions are obtained by means of the simple 

 medicine dropper device (Fig. 1) described in Vol. Ill, No. 8, p. 962 

 of the Journal. 



2. Motile organisms may be readily obtained for the test by 

 keeping at hand pure cultures of typhoid bacilli in hermetically 

 sealed tubes. When a test is to be made a fresh agar or bouillon 

 culture is made from the stock culture and kept in the incubator for 

 eighteen to twenty-four hours. It was found that the temperature of 

 a fairly warmed room produced just as good if not better results 

 than the incubator. The author deems the bouillon culture unsatis- 

 factory and has adopted the following medium : An agar culture is 

 kept in the incubator or at room temperature for twelve to eighteen 

 hours, when two or three loopfuls are transferred into bouillon until 

 a marked turpidity results, or a small quantity of bouillon is added 

 to the agar culture and enough of the growth scraped off to produce 

 a uniform cloudiness. The latter course is preferable and if care- 

 fully followed the " natural " clumps so frequently observed in 

 bouillon cultures (Fig. 2 B) are entirely avoided. 



3. The third problem is met by using a slide with two concavities Fig. i. 



(Fig. 3), around the edges of each of which 

 is a r^ng of vaseline. On each of two clean 

 cover-glasses is deposited a loopful of the 

 culture ; to one a loopful of the blood, diluted 

 1:20 to 1:40, is added, while the other serves as 

 a control. The behavior of the bacilli on each 

 cover may be readily observed. If the reaction 

 is positive the bacilli on the test 

 cover will gather in clumps of two, 

 three or a dozen and will soon lose 

 their motility (Fig. 2 D), while in the 

 pseudo-reaction only a few clumps 

 will form, the rest of the bacilli re- 

 maining separated (Fig. 2 C). 



4. The time given to determine whether a reaction is positive 

 or negative varies greatly with different bacteriologists. Dr. 

 Robin proposes the adoption of a uniform limit and offers the 

 following: Dilution 1:10, time limit 5 to 15 minutes; 1:20, 15 

 to 20 minutes; 1:40 to 1:100, .'JO to (JO minutes; 1:100 to 1:200, 

 1 to 2 hours. That is, if within the specified time a consider- 

 able number of bacilli are found actively motile or, if dead, fail to 

 arrange themselves in clumps, the reaction is negative, irrespect- 

 ive of the clumps which have already formed. c. w. j. 



Fig. 



