340 THE ALCALIGENES DYSENTERY TYPHOID 



serum were diluted many times. Grunbaum and later Widal applied 

 this principle in the diagnosis of typhoid fever. It is now recognized 

 that the principle involved is a general one for certain kinds of bac- 

 teria, and the Gruber-Durham-Grunbaum-Widal reaction is used 

 practically in the diagnosis of several diseases. The sera of such 

 animals frequently contain agglutinins which are active even in 

 dilutions of IO| Q OU or even higher. Specific lysins are also produced, 

 which in dilutions of iJ to jyVo will dissolve (and kill) typhoid bacilli. 



1. Collection of Blood for the Agglutination Test. Dried blood, blood 

 serum, blister fluid, or whole blood may be used for this reaction. 



(a) Dried Blood. A generous drop of blood is dropped upon a 

 thin sheet of aluminum or upon clean, glazed paper, and allowed 

 to dry. The advantages of dried blood are: (1) it is easily obtained 

 by making a puncture in the ear of the patient and collecting a drop 

 of blood; (2) it does not lose its agglutinating properties readily; 

 (3) it is not readily contaminated; and (4) the blood may be 

 removed quantitatively after it is dried (scaled off), weighed and 

 then diluted to the desired degree as accurately as blood serum. The 

 disadvantages are: (1) flies will readily remove a film of dried blood; 

 and (2) typhoid bacilli are rarely found in blood clots. There is, 

 however, very little danger of spreading typhoid in this way. In 

 practice dried blood is diluted with physiological normal saline solu- 

 tion to a pale rose color, which corresponds to a dilution of 1 to 20. 

 This dilution is somewhat inaccurate and anemic bloods introduce a 

 disturbing factor. This method of dilution, however, is sufficiently 

 accurate for all except unusual cases, and it is a method generally 

 used in routine board of health examinations. 



(6) Blood Serum. A few drops of blood are collected in a capillary 

 pipette or small test-tube and allowed to clot. The serum is removed 

 and diluted accurately with salt solution. The advantages are: (1) 

 the accuracy with which dilution may be made; and (2) the ease 

 with which serum is obtained. The disadvantages are: (1) that 

 blood serum is readily contaminated; and (2) it does not keep well, 

 it deteriorates. Blood serum is the best for accurate work. 



(c) Blister Fluid. This possesses no advantages over blood serum. 

 It is somewhat more difficult to obtain and probably somewhat less 

 accurate than blood serum. 



(d) Whole Blood. Aside from clotting, whole blood is as reliable 

 as blood serum, so far as accuracy of dilution and potency of agglu- 

 tinins is concerned. It must be remembered, however, that the red 



