TYPHOID FEVER. 383 



The thorough investigations of Wyatt Johnston and 

 his associates in Montreal have shown that reliable reac- 

 tions can only be secured when the cultures employed are 

 of an ordinarily virulent typhoid bacillus, and are grown 

 in an alkaline medium for about twenty-four hours. 



I prefer fresh agar-agar cultures, distributed throughout 

 sterile clean water, rather than bouillon cultures, because 

 of the larger number of bacteria in the former, the con- 

 sequently greater number of agglutinations formed, and 

 the readiness with which they are found upon micro- 

 scopic examination. It is necessary, however, to make 

 a microscopic examination of the diluted culture before 

 adding the serum or blood, in order to be sure that there 

 are no natural clumps of bacteria present to simulate the 

 specific agglutinations. This is of great importance. 

 The natural clumps of bacilli are more apt to occur in 

 cultures grown upon fresh, moist agar-agar than upon 

 that kept for a short time until the surface has become 

 partially dried. The chief difficulty experienced in 

 making the test seems, at present, to reside in the prepa- 

 ration of the blood in accurate dilution i. e. securing 

 it in measured amounts. 



The original method of Widal, to collect about 5 c.cin. 

 of blood in a test-tube by the introduction of a hypo- 

 dermic needle into a vein, is a rather more serious and 

 disturbing operation than most patients care to undergo 

 for purposes of diagnosis. 



Blood dried upon paper, as suggested by Johnston, or 

 upon glass, while extremely convenient for transporta- 

 tion, is not susceptible of accurate dilution for quantita- 

 tive estimation. 



Cabot has successfully made dilutions with a medicine- 

 dropper, by using one drop of blood and as many drops 

 of culture, dropped from the same instrument, as were 

 necessary for the desired dilution. This method seems 

 to be very practical, but can only be employed at the 

 bedside, or where it is not necessary to keep or trans- 

 port the blood. 



