LYSINS 157 
substance present in unheated normal and immune sera, Bordet ga^•e 
the name "alexin;" to the thermostabile specific substance in immune 
sera he ^ave the name "substance sensibiHtrice." He regarded the 
"substance sensibiHtrice" as a sensitizer or mordant which made bac- 
teria or blood cells vulnerable to the ferment-like or digestive acti(m of 
the "alexin." 
Ehrlich and Morgenroth' studied the phenomena of hemolysis in 
great detail and demonstrated by Aery careful and ingenious experi- 
ments that the phenomena observed by Bordet were fundamentally 
correct. They showed: 
1. That inactivated specific hemolytic serum (heated to 55° C.) 
was absorbed by the homologous red blood cells, and that these 
"sensitized" cells, separated from the serum after a few hours and 
washed carefully, were readily hemolyzed when resuspended in salt 
solution to which was added a small amount of fresh, unheated, normal 
guinea-pig serum. 
2. The supernatant residual fluid, from which the red blood cells 
had removed all the immune body, was incapable of causing hemolysis 
of the homologous red blood cells when fresh normal serum was added 
to it. The erythrocytes, in other words, quantitatively removed the 
thermostabile "substance sensiblitrice" from solution. 
3. If normal sera were allowed to remain in contact with the same 
red cells for an equal length of time, and these red cells were then 
removed by centrifugalization and resuspended in salt solution con- 
taining normal fresh serum, no hemolysis took place, leading to the 
conclusion that the thermolabile substance (alexin of Bordet) is not 
removed from solution by erythrocytes. Apparently alexin is not 
bound or anchored directly to the red cells. 
4. Finally, it was shown that inactivated immune serum, red 
blood cells and fresh normal serum could be maintained at 0° C. 
without apparent hemolysis. At 37° C. the same solution soon 
exliibited complete hemolysis. Thus, at the lower temperature, the 
normal serum failed to cause hemolysis. If the mixture maintained 
at 0° C. were centrifugalized, however, after some hours, and the 
red blood cells washed thoroughly and resuspended in salt solution, 
hemolysis promptly occurred when a small amount of normal serum 
was added to the suspension, thus showing clearly that the inacti\'ated 
immune serum was bound or anchored by the red blood cells at 0° C, 
even though activation did not take place. 
Ehrlich substituted the term "amboceptor" for Bordet's term 
"substance sensibiHtrice" and complement for the term "alexin," 
and conceived that the immune body— amboceptor— consisted 
essentially of two combining or haptophore groups— one the cyto- 
philic group, possessing a specific combining power for the specific 
cell (bacterium or erythrocyte), the other, complementophilic group, 
1 Berlin, klin. Wchnschr., 1899, 36, 6, 481. See Ehrlich: Collected Studies on 
Immunity, translated by Bolduan, 1910. 
