Experiments are presented which demonstrate that precipitin remains unaltered quantitatively and qualitatively in the guinea-pig for several days and that it reacts in the animal body with its antigen in exactly the same manner as it does in the test tube. The experiments furnish further evidence that precipitin and “sensitizin” are identical.
The phenomenon of “anti-sensitization” (Weil) is not due to the action of anti-antibodies. It is a non-specific effect the nature of which is obscure.
Passive sensitization with washed specific precipitates has generally failed in our hands.
The sodium carbonate extract or solution of specific precipitates do not contain free antigen but represents the whole precipitate in solution.