AGGLUTINATION 203 



A number of small diameter tubes each containing 1, 2, 3, 4, or 5 c.c. of 

 bouillon, are kept on hand. When a test is to be made, one adds a drop of 

 the serum to each of these tubes and then inoculates each with a typhoid cul- 

 ture. The tubes are then kept at incubator temperature for from four to six 

 hours. At the expiration of this time it may be seen at a glance in which tubes 

 agglutination has taken place, since these will be unclouded and the floccules 

 will be seen on the bottom. The first tube has a dilution of 1 : 20 ; the second, 

 1 : 40, etc. 



Johnston was the first to show that a drop of blood allowed to 

 dry on non-absorbent paper, may be transported any distance and 

 kept indefinitely and still be capable after solution in water of giving 

 the agglutination test. However, accuracy in dilution is not reached. 

 The reaction may be observed in a hanging drop under the microscope 

 when only one drop of blood is available. 



Agglutinins exist not only in the blood, but in other fluids of the 

 body. The agglutinating power of the urine in the same individual 

 is variable not only from day to day, but from hour to hour, and is 

 always feeble compared with that of the serum. Serum obtained by 

 blisters has a relatively high agglutinating value. That of the bile is 

 marked. Pus from typhoid abscesses markedly agglutinates. Agglu- 

 tinins may pass from the mother to the fetus and to the nursing child. 

 Typhoid serum may be treated with formaldehyd in 40 per cent, solu- 

 tion and kept quite indefinitely without loss of its agglutinating 

 property. However, the use of antiseptics is not necessary to preserve 

 agglutinating sera. A highly active serum will retain its agglutin- 

 ative action after it has become putrid from bacterial contamination. 

 Dilute mineral acids decrease the agglutinating property of typhoid 

 sera, but when the contact has not been prolonged, full activity may 

 be restored by neutralization. Alkalies act similarly. App arently the 

 agglutinins are not altered by either pepsin or trypsin. In experimental 

 animals, sera can be obtained which will agglutinate typhoid bacilli 

 in dilutions as high as 1 : 1,000,000 and colon bacilli, 1 : 2,000,000. 



Quantitatively the agglutinins are specific, but in order to be so 

 considered they must be active in high dilutions. A positive diagnosis 

 of typhoid fever should not be made unless the serum acts decidedly 

 in a dilution not less than 1 : 50, and even in this dilution there is a 

 rare chance of mistake. A paratyphoid serum may agglutinate typhoid 



