26 LECTURES ON IMMUNITY 



for haemoglobin, viz. 48,000. For the antitoxins it may be 

 still some ten or one hundred times higher. 



As the antitoxins diffuse about ten times more slowly 

 than the toxins, it seems theoretically possible to separate 

 them by diffusion. The first experiment in this direction 

 was done by Martin and Cherry. 1 They prepared 60 c.c. 

 of an innocuous mixture of diphtheria- toxin, containing 

 three hundred lethal doses and its antitoxin, and heated it 

 for two hours at 30 C. This mixture was allowed to filter 

 under pressure (50 atm.) through a film of gelatine sup- 

 ported by a Pasteur-Chamberland filter. The filtrate con- 

 tained chiefly water, which passes through the filtrum very 

 much more rapidly than the toxin or the antitoxin. This fil- 

 trate was examined and found to contain per cubic centi- 

 meter less than 3 and 5 per cent respectively of the poison 

 in one cubic centimeter of the original mixture, the poison 

 being supposed to be entirely free. Now water passes more 

 rapidly than sodium chloride through gelatine, and sodium 

 chloride about sixty-seven times more rapidly than diph- 

 theria-toxin. Hence we should expect that even if no poison 

 at all were bound, the first filtrate would contain per cubic 

 centimeter only 1.5 percent of the quantity of poison in the 

 original mixture. Later on as the original mixture by the 

 extraction of water became more concentrated, as seems to 

 have been the case in these experiments, a higher percent- 

 age might have been expected. But the conclusion which 

 has been drawn from them, that but a small part, say 5 per 

 cent, of the toxin was actually free, may not be regarded 

 as warranted by the facts. 



A similar experiment has been carried out by Craw in 



1 Martin and Cherry: Proc. Roy. Soc., 63. 420 (1898). 



