The Agglutinins 125 



tap water, and then freed from corpuscular stroma by filtration or 

 decantation. Two cubic centimeters of it are placed in a small 

 test-tube, and further diluted with an equal quantity of physiological 

 salt solution (if more water be added a precipitate of globulin might 

 take place and spoil the experiment). To such a prepared blood 

 solution, from six to eight drops of the immune serum are added. If 

 the diluted blood come from the same kind of animal as that whose 

 blood was used to immunize the animal furnishing the test serum, 

 immediate clouding takes place, and a flocculent precipitate forms. 

 The precipitate never occurs with any other blood. 



Wassermann* and Schutze prepared a test serum by injecting 

 rabbits with human blood. They tested its precipitating powers 

 upon twenty-three other kinds of blood and found no precipitate 

 except with the blood of a baboon, but the reaction in that case was 

 not nearly so marked as with human blood. 



The most interesting and one of the most important biological 

 apphcations of this phenomenon is by Nuttall, whose work, "Blood 

 Immunity and Blood Relationship" (Cambridge, 1904), should be 

 read by all who wish to study the subject for its scientific interest 

 as a means of determining the blood relationship of animals, or its 

 practical medicolegal importance in recognizing blood-stains. 

 Nuttall comes to the following conclusions: 



"(i) The investigations we have made confirm and extend the observations 

 of others with regard to the formation of specific precipitins in the blood-serum 

 of animals treated with various sera. (2) These precipitins are specific, although 

 they may produce a slight reaction with the sera of allied animals. (3) The sub- 

 stance in serum which brings about the formation of a precipitin, as also the pre- 

 cipitin itself, are remarkably stable bodies. (4) The new test can be successfully 

 applied to a blood which has been mixed with those of several other animals. 

 (5) We have in this test the most delicate means hitherto discovered of detecting 

 and testing bloods, and consequently we may hope that it will be put to forensic 

 use." 



Further perfection in the technic of the precipitation experiments 

 can be found in a paper by Nuttall and Inchley.f 



The precipitinogen is capable of acting as an antigen and the 

 injection into animals of serum containing it results in the formation 

 of anti-precipitins. 



AGGLUTINATION 



Agglutination is a phenomenon of infection and immunity in 

 which the serum or other body juice of the infected animal so acts 

 upon the infecting micro-organism as to destroy its power of move- 

 ment, and cause it to sediment in clusters in the Uquid in which it 

 is suspended. This phenomenon was first observed by Charrin 

 and Rogerf in the course of experiments with Bacillus pyocyaneus. 

 They found that when Bacillus pyocyaneus was introduced into a 

 test-tube containing the diluted serum of an animal infected with or 



* "Deutsche med. Wochenschrift," 1900, No. 30. 

 t "Journal of Hygiene," 1904, iv, p. 201. 



