1911.] 



On the Factors Concerned in Agglutination. 



423 



Experiment to Show that the Agglutinative Properties of the Middle-Piece 

 Solution are Thermostable. 

 The explanation offered in the preceding paragraph assumes that the 

 agglutinating power of an immune serum depends on the presence of two 

 thermostable substances, namely, the specific antibody and a non-specific 

 substance. It is suggested that a deficiency of the non-specific substance 

 in a greatly diluted antiserum may be made good by the addition of middle- 

 piece solution. 



Before this explanation can be accepted it is necessary to show that 

 this substance or property of the solution of middle-piece is thermostable, 

 that is to say, capable of resisting a temperature of 56° C. for half an hour. 

 The result of an experiment intended to settle this point is given in 

 Table III. 



Table III. 





Dilutions of 

 the middle- 

 piece solution. 



Fresh 

 solution. 



Middle-piece solution previously heated at 56 3 C. 







2 hours. 



4 hours. 



1 



1—10 



+ + + + 



+ + + + 



+ + + + 



+ + + + 



+ + + + 



2 



1—20 



+ + + + 



+ + + + 



+ + + + 



+ + + + 



+ + + + 



3 



1—40 



+ + + + 



+ + + + 





+ + + 



+ + + 



4 



1-80 



+ + + + 



+ + + + 



+ + + 







5 



1—160 



+ + 



+ + 



+ + 





+ 



Quantities of 5 c.c. of the middle-piece solution were heated at 56° C. for \, 1, 2, and 4 hours. 

 Parallel dilutions of each sample were then made, and of the original unheated solution. To 

 each tube, which contained 1 c.c. of diluted middle-piece solution, was added 1 c.c. of sheep cells 

 1 in 20, and 1 c.c. of a 1 in 200 dilution of hsemolytic serum. Control tubes were put up which 

 showed that neither a 1 in 200 dilution of hsemolytic serum nor a 1 in 10 dilution of middle- 

 piece was capable, when acting by itself, of agglutinating the red cells. 



Remarks on Tables III and IV. 



Prom this and similar experiments, it was determined that the capacity of 

 the solution of middle-piece to aid in agglutination was only very gradually 

 destroyed at a temperature of 56° C. ; heating for half-an-hour had a very 

 slight, or no effect at all, in reducing its activity. 



This property of aiding in agglutination can be classed as one of the 

 relatively thermostable properties of serum. It is equally evident that this 

 property of the solution of middle-piece has no connection with its hsemolytic 

 property, for the latter is rapidly lost by subjecting such a solution to a 

 temperature of 56° C. The middle-piece fraction of the haemolytic com- 

 plement is definitely thermolabile. On the other hand, whole guinea-pig 



