THE PHENOMENON OF AGGLUTINATION 



incubator for ten to twelve hours together with homologous serum, 

 will grow in long, delicate chains, like those of streptococci. This 

 form of reaction has been especially studied by Pfaundler, 11 who 

 attributed particularly delicate specificity to it. However, the 

 " Thread Reaction" of Pfaundler, as it is sometimes called, is merely 

 another manifestation of the phenomenon of agglutination and sub- 

 ject to the same laws and limitations of specificity which apply to 

 other methods. 



The purely passive role played by the bacteria in agglutination 

 is best shown by the fact that dead bacteria, killed in various ways, 

 are specifically clumped just as are the living cultures. 12 On this 

 fact depends the method spoken of as "Picker's Reaction," in which 

 emulsions of typhoid bacilli, killed by formaldehyd or carbolic acid 

 (distributed commercially), are agglutinated in small test tubes by 

 the serum of typhoid patients. The original method of Picker is 

 said to be a proprietary secret ; however, a number of other methods 

 which attain the same purpose are in use in various places. Volk 13 

 describes the method used in Vienna, and states that there carbolic 

 acid is used to kill the cultures. Similar to this is the method de- 

 scribed by J. H. Borden, 14 who proceeds as follows : 



The bacilli are grown on agar slants in large tubes for 24 hours. 

 They are then washed from the medium with a sterile mixture of 

 salt solution 450 parts, glycerin 50 parts, and 95 per cent, carbolic 

 acid 2.5 parts. After this solution has been kept a week it becomes 

 translucent and by this time the bacilli are dead. The preparation is 

 then ready for use and can be kept a long time in dark bottles in a 

 cool place. Borden very carefully controlled this bacterial emulsion 

 with positive and negative typhoid sera and found it reliable. The 

 great advantage of all these methods, of course, consists in the possi- 

 bility of furnishing the general practitioner with materials for clini- 

 cal agglutination tests in which the necessity of preserving and sus- 

 pending living cultures is eliminated.- 



The facts which we have just considered tend to show that agglu- 

 tination is not a vital phenomenon 15 dependent in any way upon 

 the living nature of the bacterial cell, but, like other phenomena of 

 antigen-antibody reactions, a purely chemical or physical process in 

 which the substance of the bacterial cell enters specifically into rela- 

 tion with the agglutinating factor of the serum. In uniformity with 

 other analogous reactions the antigenic substance is here spoken of 

 as "agglutinogen," the antibody as "agglutinin." 



11 Pfaundler. Wien. kl Woch., 1898, and Centralbl. f. Bakt., I, Vol. 23, 

 1898. 



12 Bordet. Ann. Past., Vol. 10, 1896. 



13 Volk. "Kraus und Levaditi Handbuch," Vol. 2. 



14 Borden. Medical News, N. Y., Mar., 1903. 



15 Bordet. ^nn. Past., Vol. 10, 1896. 



