214 



Mr. L. S. Dudgeon. On the Presence of [Feb. 18, 



Same serum saturated with same undiluted normal red cells for one and 

 a, quarter hours at 37° C. ; mixture centrifuged. 



Clear fluid + Normal red cells. 

 No agglutination. 



When the immune typhoid serum was saturated with the typhoid red cells 

 in a similar manner to the above, the clear fluid agglutinated normal red 

 cells as before. It must be pointed out here that although saturation of 

 a serum with suitable red cells will render the serum specifically inactive, 

 and that saturation with inactive red cells will have no effect, yet, if the 

 -serum is capable of agglutinating the active red cells from two different 

 diseases, saturation with one class of red cell may fail to render the serum 

 inactive for the other red cells. Further work is being done on this 

 important point at the present time. 



The Effect of Saturating an Immune Serum with Melanin. 



It has been shown conclusively in this paper that if you saturate typhoid 

 serum with suitable red cells you remove the haem-agglutinins, but leave the 

 bacterial, and vice versd. 



Other experiments were undertaken for the purpose of ascertaining whether 

 it would be possible to remove or greatly diminish the hsem- or bacterial- 

 agglutinative action of the serum by means of melanin as Mr. Shattock and 

 I have found to occur in experiments on phagocytosis.* Immune serum 

 (typhoid) was saturated with sterile melanin for 12 hours at 37° C. The 

 resulting fluid obtained after centrif ugalisation was still capable of agglutinating 

 typhoid bacilli and suitable red cells as the unsaturated serum, and also to 

 the same degree. 



The Effect of Saturating a Scrum with Heated Reel Cells. 

 In the experiments about to be referred to, it has been shown that it is 

 possible to remove the agglutinative properties of a serum by saturating it 

 with heated red cells. The red cells for this purpose are thoroughly washed 

 in the usual manner, and definite proportions from the deposit of red cells 

 obtained at the end of the final process of centrifugalisation are put in suitable 

 tubes with a small quantity of physiological salt solution ; the tubes are sealed, 

 placed in a tube of water at a definite temperature, and then put into a water 

 bath at the same temperature as the tube of water. By this means, and this 



* S. G. Shattock and L. S. Dudgeon, ' Koy. Soc. Proc., ! B, vol. 80, 1908, "Observation* 

 on Phagocytosis by means of Melanin and the Comparison of the Opsonic Index with the 

 Ha?mo-phagocytic Index." 



