510 7 Captain A. G. McKendrick. [Nov. 30, 
present itself, if only a very small number of them was present. In 
agelutination experiments, if the organisms were few in number, a portion 
of y would remain unabsorbed. | 
IX. Toxins and Antitovins—Ehbrlich has postulated that the toxin 
molecule has two receptors, a toxophorous, which is comparatively thermo- 
labile, and a haptophorous, which is thermostable. Arrhenius has stated 
that these receptors may be considered to belong to two different molecules. 
I shall go a step further, and by imitating the chief characters of toxins, 
and their neutralisation by antitoxins, show that these two factors are 
probably amboceptor and complement, and that the antitoxin is an anti- 
am boceptor :— 
(a) A primary characteristic of toxins is that different samples may agree 
in their minimal lethal dose (M.L.D.), whilst they disagree in the amount of 
antitoxin necessary for their neutralisation. 
Fig. 3 isa form of chart obtained as on Chart 1, z = effect (in Chart 1, z 
signified complete lysis, z.e. death of the cell. It may now be considered as a 
“ Jethal ” line). 
Toxins consisting of—- 
ay + ex, CY + gx, 
by + fx, dy + ha, 
all have the same lethal effect, but the quantity of an anti-amboceptor 
requisite for neutralisation would be a, 0, ¢, d, equivalents respectively. 
(6) A second characteristic is that a toxin which has deteriorated in lethal 
effect still requires the same amount of antitoxin to neutralise it. This is 
obviously a corollary of (a). 7 
For instance, let a toxin dy+ha deteriorate to dy+ex; d equivalents of 
anti-amboceptor will be required for neutralisation of both the fresh and the 
deteriorated states, but the lethal effect will have been much diminished. 
As amboceptor has been considered to remain constant during deterioration, 
