9 6 



THE PRINCIPLES OF IMMUNOLOGY 



FIG. ii. The nip- 

 ple pipette for 

 making mixtures 

 of fluids and bac- 

 teria] suspension. 

 The pencil mark is 

 seen a short dis- 

 tance above the 

 tip. 



Tube 



I 

 2 



3 



4 

 5 



tion is also a relative matter, as is shown in the group 

 reactions, and if electric phenomena play a part in spe- 

 cificity they are more delicate than can be demon- 

 strated by present chemical or electrical methods. 

 Bordet, who laid no emphasis on the electrical reac- 

 tions, thought that the process of sensitization of bac- 

 teria by agglutinins is in essence a denaturing of the 

 bacterial proteins, and that the specificity of the process 

 depends on the degree of denaturation. 



The Dreyer Test. The Widal test has been described 

 (page 85). This test has been of the greatest service in 

 the diagnosis of typhoid and paratyphoid fevers but the 

 introduction of vaccination on a large scale has reduced the 

 value of the test as a diagnostic sign of actual disease, be- 

 cause vaccinated individuals give a positive test. Dreyer 

 studied the course of agglutination in typhoid and paratyphoid 

 fevers, and found that the agglutinative titer of the blood 

 follows, during the course of the disease, a fairly regular curve, 

 increasing to the third week and then declining. Although 

 the titer may be higher at the beginning of the disease in 

 vaccinated individuals than in others, the titer follows the 

 same general curve. Of more importance is the differentia- 

 tion between typhoid and other infections in the vaccinated. 

 This has been of the utmost importance in the World War 

 in distinguishing between febrile disease, such as trench fever 

 or malaria, and typhoid or paratyphoid. The test is made by 

 the macroscopic method for agglutination, and must be re- 

 peated at weekly intervals in order to determine the curve 

 of agglutinins. Not infrequently the first test may show a 

 titer so much higher than occurs after vaccination that a 

 presumptive diagnosis is justifiable. Under war conditions 

 the transfer of patients often made it necessary to perform 

 the tests in several different laboratories, and to provide for 

 this the Oxford Standards Laboratory prepared emul- 

 sions of the bacilli for distribution. For this purpose 

 the organisms were grown for twenty-four hours in pep- 

 ton veal broth, then shaken well and o.i per cent, for- 

 malin (40 per cent, formaldehyde) added. The culture was 

 stored at 2 C. and shaken frequently during four or 

 five days. At the end of this time it was usually sterile. 

 It was then diluted to standard opacity by means of salt 

 solution, to which was previously added o.i per cent, 

 formalin. It was further standardized as to ^agglutina- 

 bility and labeled with a factor so as to provide means 

 whereby tests in different laboratories could be estimated 

 on the same basis. 



The blood for the test can be obtained in a Wright 

 tube, but it is preferably taken from the cubital vein 

 into a centrifuge tube, so as to provide a fairly large 

 amount of serum. In order to make the method appli- 

 cable in laboratories where graduated pipettes are ^ not 

 available, Dreyer made all the dilutions with a nipple 

 pipette of drawn-out glass tubing similar to that illus- 

 trated in Fig. n, except that the drawn-out part is wider 

 and shorter. Three rows of 7 x 75 mm. test tubes are then 

 set up and further dilutions made according to the follow- 

 ing scheme; 



Water Serum Bacterial suspension Dilution equals 



.o drop 10 drops 15 drops 1-25 



5 drops 5 drops 15 drops 1-50 



8 drops 2 drops 15 drops 1-125 



9 drops i drop 15 drops 1-250 

 10 drops o drop 15 drops control 



