374 THE ALCALIGENES— DYSENTERY— TYPHOID GROUP 
products; of these, lysins, agglutinins, opsonins and precipitins have 
been carefully studied. The method of fixation of complement and 
the ophthalmo reaction have received less attention. 
The lysins, which appear early in the course of the disease, dissolve 
typhoid bacilli, but not other bacteria, at least in the dilutions ordi- 
narily used. It is probable that the lysins not only dissolve typhoid 
bacilli in vitro, they destroy the organisms in the blood stream as well,^ 
liberating endotoxins which play a prominent part in the production of 
the febrile reaction. 
Agglutinins are formed in the majority of cases, which will clump 
typhoid bacilli. The significance of agglutinins in the typhoid complex 
is not definitely established. 
The opsonic index of the serum of immunized animals and of clinical 
cases of typhoid fever in man appears to be increased, but available 
methods of measuring the opsonic index do not furnish information 
consistent enough to warrant definite conclusions. 
The reaction of fixation of complement has been used diagnostically 
in a limited number of cases. The technical skill required to elicit 
satisfactory results has doubtless interfered with its general application. 
The agglutination reaction is by far the most commonly used anti- 
body reaction employed in the diagnosis of typhoid fever. 
The ]]'idal Reaction.— Historical.- — Gruber and Durham appear 
to have first demonstrated that the sera of animals immunized to 
typhoid bacilli would agglutinate the typhoid bacilli, even if the 
serum were diluted many times. Griinbaum 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-Griinbaum-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 yoTFo" o^ even higher. Specific lysins are also produced, 
which in dilutions of y'W'o to t¥Fo will dissolve (and kill) typhoid bacilli. 
1. Collection of Blood for the Agglutination Te^L— 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 disad- 
vantages are: (1) Flies will readily remove a film of dried blood; 
and (2) typhoid bacilli are occasionally found in blood clots; there is, 
however, very little danger of spreading typhoid is this way. In 
1 Coleman and Buxton: Medical and Surgical Report of Bellevue and Allied Hos- 
pitals, 1909-1910, 4, 46. 
