192 G G. Heslop; 



Conglutinin. 



It was found, when carrying out tests with the alcoholic ex- 

 tract of sub-epidermal tumour tissue, that, while complement 

 fixation occurred with known positive sera, the reaction was liable: 

 to become masked by a subsequent haemolysis of the sensitised 

 red blood cells added as an indicator. 



Different positive sera exhibited this tendency to bring about 

 final haemolysis in varying degrees — i.e., some were more prone 

 to it than others — but as haemolysis invariably occurred, it was 

 evident that there was contained in the test serum some element 

 which was capable of acting upon the sensitised red blood cells 

 after fixation of complement had occurred. This haemolysis 

 made it exceedingly difficult to differentiate between the reaction 

 given by a known negative serum, and a known positive serum,, 

 because, in some cases, the length of time between the haemo- 

 lysis with a negative serum, and the haemolysis with a positive: 

 serum was only a matter of a few minutes. 



It was also noticed that in the final test, on the addition of 

 the sensitised red blood cells, the red blood cells were almost im- 

 mediately " agglutinated " and sedimented more or less com- 

 pletely at the bottom of the tubes. 



It was thought at first that this " agglutination " of red blood- 

 cells could be made use of for diagnostic purposes, but it was 

 very soon demonstrated that, while, as a general rule, the pheno- 

 menon occurred earliest in the tubes containing negative sera, 

 certain of the tubes containing positive sera also showed early 

 " agglutination," of the red blood cells. 



On the other hand, some tubes containing negative sera showed 

 a delayed " agglutination " of the red blood cells. A similar de- 

 layed " agglutination " was also shown in certain of the tubes 

 containing positive sera. 



It was thus evident that this phenomenon was of no diagnostic 

 importance, because its appearance depended upon some sub- 

 stance which was present in all the bovine sera tested, although 

 present in a varying amount. This substance was not more 

 often present in negative sera than in positive sera, although, as 

 a general rule, the reaction appeared earlier with negative sera. 



Bordet and Gay (1906) (3) in studying the action of inacti- 

 vated bovine serum upon sensitised corpuscles in the presence of 

 complement, demonstrated the presence in bovine serum of a 

 specific substance which they first referred to as "colloid sub- 



