180 TYPHOID FEVER. 



have had the disease, when mixed with young cultures of 

 Eberth's bacillus, has the property of arresting the active 

 motion of the bacilli, and causing their agglutination or 

 clumping. This power resides in the serum, and is due to a 

 substance called agglutinin. 



Widal inaugurated the blood-test for typhoid fever, and sug- 

 gests that to 1 c.c. of bouillon culture, not more than twenty- 

 four hours old, and grown at a temperature of 35 C., 0.10 c.c. 

 of the serum to be tested be added. The serum may be 

 obtained either by allowing the drawn blood to coagulate, or 

 by means of a small blister. In the space of from five to 

 ten minutes all motion of the bacilli is arrested, and these 

 come together, forming peculiar clumps. This clumping may 

 be seen both in the hanging drop, and even by the naked eye 

 in culture- tubes. Ordinarily the hanging-drop method is 

 adopted, as it requires much less serum, and is therefore less 

 injurious and vexatious to the patient, 



Wyatt Johnston's Dried Blood Method. This observer has 

 demonstrated that the same reaction may be obtained by the 

 use of dried blood instead of fresh serum, and that even after 

 the blood has been dried for several days or weeks it still 

 retains its agglutinating power. The procedure in detail is as 

 follows : 



A drop of the blood to be tested is obtained from the finger 

 or lobe of the ear and allowed to dry on a clean slide. AVith 

 a platinum wire a few loopfuls of sterile water are mixed with 

 the dried blood and the same is diluted until about of the 

 same color as normal blood. One loopful of this blood mixt- 

 ure is added to 40 or 50 loopfuls of a bouillon culture of 

 the Bacillus typhosus twenty hours old, on a cover-glass, and 

 a hanging drop made in the usual way. In the course of a 

 half- to one hour, if the blood comes from a case of typhoid 

 fever of sufficient duration, not less than six or seven days, 

 cessation of motion and clumping of the bacteria in the 

 culture drop will have been completely effected. 



In the experience of the author in the Municipal Labora- 

 tory of New Orleans with more than 12,000 cases, this test 



