106 THE PRINCIPLES OF IMMUNOLOGY 



Gengou reported agglutination and hemolysis by means of such chemi- 

 cal precipitates as calcium fluoride and barium sulphate, but in these 

 instances serum served to prevent agglutination. This appears to be 

 another example of protective colloidal action. According to Girard, 

 Mangin and Henri, the red cells carry electro-negative charges, but 

 agglutination has been produced by colloids regardless of the electrical 

 charge they carry. We, in collaboration with Hanzlik, have exam- 

 ined a wide variety of colloids and have determined that many of 

 those which produce thrombosis upon intravenous injection into animals 

 also produce agglutination in the test tube. 



Conglutination. Bordet and Gay, as well as Muir and Browning, 

 independently described in 1908 the phenomenon of conglutination an 

 agglomeration of corpuscles in the presence of two normal sera. The 

 result of this reaction is the agglutination of corpuscles, but what is 

 known of its mechanism makes it advisable to consider the phenomenon 

 after the discussion of hemolysis (see page 126). 



PRECIPITATION 



Introduction. The discovery of agglutination led to the discovery 

 by R. Kraus in 1897 of the precipitin reaction. His problem was to 

 determine whether or not agglutinating sera would act in any way on 

 extracts of bacteria, and in his work with typhoid bacilli and cholera 

 vibrios he found that the addition of the specific antisera to the bac- 

 terial extracts led to the formation of a precipitate and that this 

 reaction is specific. This was confirmed by Nicolle. Previously Widal, 

 Levy and Bruns had shown the converse, namely, that filtrates of 

 typhoid and cholera cultures upon injection led to the formation of 

 agglutinins. In 1899 Tchistovichs published the results of his work 

 with horse serum and eel serum, demonstrating the formation of 

 specific precipitates when the serum of rabbits previously inoculated 

 with these sera was added to the antigenic sera. Bordet confirmed 

 this with chicken serum and later showed that cow's milk upon injec- 

 tion induces the formation of a specific precipitating serum for the 

 casein of the milk. Kraus states that previous to the publications of 

 Tchistovitchs and of Bordet he had also, in collaboration with Winter- 

 berg and E. P. Pick, experimented with proteins of animal origin. 

 Fish demonstrated the specificity of various milk antisera for their 

 respective antigens. The reaction was enlarged in scope for various 

 other animal proteins. Kowarski showed that the reaction is specific 

 for higher vegetable proteins as well as for those of bacteria. Certain 

 authors have claimed that peptones, globulins, albumoses and other 

 protein products are antigenic in a similar manner, but the weight of 

 evidence is that the whole protein molecule is necessary. A recent 

 review of the literature on this subject by Fink has shown that state- 

 ments in regard to the proportion of the entire protein molecule neces- 

 sary to take part in the reaction are confusing and obscure. Frequently, 

 instead of testing against the decomposition product itself, the serum 

 obtained by its use has been tested against the entire protein molecule. 



