170 Dreyer and Douglas. Velocity of Reactio7i in [Nov. 16, 



by comparing its translucency with that of the standard culture, a method 

 which allows of great accuracy. 



To the 100/1 N emulsion was added 1 per cent, of ordinary commercial 

 40 per cent, formaldehyde. This stock emulsion was kept in an ice chest 

 in the dark at from 0° to 2° C. Usually a 10/1 N emulsion was used 

 for the absorption of the agglutinin, the stock emulsion being suitably 

 diluted with sterile 0'85 per cent. NaCl for each experiment. Control 

 experiments were made to ascertain that formalin in this amount did not 

 give appreciable differences in the quantity of agglutinin absorbed. The 

 experimental details on this point will be published in a later paper. 



The serum used, unless otherwise stated, was obtained from a goat 

 immunised with the stock Bacillus coli mentioned above, and was suitably 

 diluted with sterile 0"85 per cent. NaCl. All apparatus used was carefully 

 cleaned and dry sterilised. All measurements and dilutions were carried out 

 with accurately graduated glass pipettes. For investigating the absorption 

 of agglutinin by bacteria, 4 c.c. of the emulsion of the corresponding bacilli 

 were added to 4 c.c. of a given dilution of serum. The tubes were then at 

 once shaken and left to stand for various lengths of time. 



Experiments were undertaken at low temperature (1° to 2° C), at room 

 temperature (15° to 17° C), and in one case at 37° C, room temperature 

 being that to which preference was given, because here no, or only slight, 

 alteration in the temperature took place during the time of centrifugalisation, 

 while with the experiments at 1° to 2° C. it was found impracticable to 

 prevent the temperature from rising during this period, as also to prevent 

 a fall in temperature if the experiments were carried out at 37° C. 



A special high speed centrifuge by Burmeister and Wain, I'un at a speed 

 of 7200 revolutions per minute for 10 minutes, was used for the separation 

 of the bacteria from the fluid. The clear supernatant fluid was decanted 

 and kept in the dark at a temperature of 0° to 2° C. until it was convenient, 

 on the same or the following day, to estimate the amount of agglutinin it 

 contained. 



Tlie measurements of the agglutinin content of the various fluids were 

 carried out l)y Dreyer's modification* of the method originally proposed by 

 Madsen and Jorgensen.f 



Tlie nietliod adopUul for the estimation- of agglutinin is as follows: — 

 Test-tulies 7 cm. long and 1 cm. in diameter were arranged in sets or series 

 of 13, and into each tube were measured out the following quantities of the 

 various fluids employed (Table 1) : — 



♦ Dreyer and .Jex-Hlakc, 'Trans. Koyal Djinisli Academy,' 1005. 



+ ' Festskrift vcd Inflviitlnc af Stati-nH Sc'i iniiiiiK( itut, ( Io])tinliaf,'C'n,' 1902. 



