TYPHOID FEVER 77 



that the blood clumps only in a dilution of i in 20 on one 

 day, and in a dilution of i in 100 three days later, this affords 

 a certain proof that the reaction is due to a present attack 

 of typhoid fever, and is not due to one which took place at a 

 previous date. This investigation should be entrusted to an 

 expert bacteriologist, and plenty of blood sent on each occasion. 

 A negative result may mean : 



1. That the patient is not suffering from typhoid fever. 



2. That he is suffering from typhoid fever, but the date is too 

 early for the appearance of the reaction. The reaction sometimes 

 occurs on the fifth or sixth day, usually after the tenth day, and 

 in all but a very small number of cases before the end of the 

 second week. If the onset of the disease (as far as it can be 

 fixed) is less than this, the examination should be repeated after 

 two or three days. 



3. In a very small number of cases the reaction is delayed still 

 further, and if the patient dies may not occur at all. These cases 

 are usually severe ones, and do not present any difficulty in 

 diagnosis. Sometimes the reaction is delayed well into the con- 

 valescence in mild attacks, but this is exceedingly rare. 



Macroscopic Method. 



The macroscopic method can be carried out with a young living 

 culture on agar, or with an emulsion of dead bacilli. The technique 

 is not so difficult as in the previous process, and no apparatus is 

 required other than a piece of narrow glass tubing, from which to 

 make pipettes. 



Requisites. — i. A young culture on agar, and some normal 

 saline solution ; or a dead emulsion of typhoid bacilli. 



2. Special glass pipettes. These are to be made from a piece 

 of glass tubing which should not be more than i inch in internal 

 diameter and about lo inches long. The central 2 inches of this 

 tube are to be heated in a flat gas flame until thoroughly softened, 

 then withdrawn, and then the two ends are to be drawn steadily 

 apart. The softened portion is to be drawn out into a long, narrow 

 portion (rather thicker than a vaccine-tube) about 6 inches long 

 and of nearly uniform diameter. The full diameter of the tube 

 should pass rapidly into this narrow portion ; it should not taper 

 gradually (Fig. 14, c). The two pipettes thus obtained are to be 

 broken apart, leaving about 3 inches of the narrow tubing attached 

 to each. The wide end of the tube is to be plugged fairly firmly 



