76 CLINICAL BACTERIOLOGY AND HEMATOLOGY 



may be watched under the microscope or by the naked eye, the 

 technique differing in the two cases. The macroscopic method is 

 in every way the more satisfactory, if the method used, or any 

 simple modification thereof, be followed. It is a good plan for 

 the student to familiarize himself with the appearances seen in 

 the microscopic method, and for that reason it will be described 

 here. But in practice the convenient, easy, and accurate pipette 

 method has almost entirely replaced it. 



The technique in either case is readily learnt, and can be 

 carried out with very little difficulty if the materials are at hand. 

 But the test is one which it is seldom advisable for the home 

 worker to attempt, as it requires a young culture of typhoid 

 bacilli. We shall, however, describe the process, as some may 

 carry it out during an epidemic, or if they are living where they 

 have not access to a public laboratory. The process has now 

 been greatly facilitated by the demonstration of the fact (by 

 Widal) that the reaction is given with dead cultures of the bacilli. 

 These cultures can be obtained from any bacteriological laboratory, 

 and will keep fairly well. They can be bought commercially, but 

 most of the samples I have seen are far too weak and almost 

 inert. They are prepared by adding 4 or 5 c.c. of the following 

 fluid to an eighteen-hours-old culture of typhoid bacilli, scraping 

 off the growth, pipetting the emulsion into a sterile test-tube, and 

 heating to 60° C. for half an hour to insure sterility : 



Normal saline solution (o'8 per cent.) 450 c.c. 



Carbolic acid (liquefied) i-25 c.c. 



Glycerin 50 c.c. 



Boil and allow to cool immediately before use.* 



The bacilli gradually separate from an emulsion prepared in 

 this way, but are distributed throughout the fluid by shaking. 

 With a supply of this culture at hand the practitioner can apply 

 the test at home without difficulty. 



Collect the blood from the ear, as described on p. 35, taking 

 care to get a Wright's pipette about half full. The test may be 

 applied to a dry drop of blood, but in this case there is no possi- 

 bility of making an accurate dilution, and unless a fair quantity 

 of serum is at hand it is impossible to perform the test by the 

 macroscopic method. 



If a pipette is not at hand, it is easy to manufacture one out of 

 any piece of glass tubing which may be available. 



* J. H. Borden, Proc. N. Y. Path. Soc, 1904. 



