418 



INFECTION AND RESISTANCE 



of typhoid bacilli could be successfully used if the time of exposure at 

 37 C. was prolonged.) 2. If sensitized bacteria are used an excess 

 of sensitization, beyond a definite limit, weakens the formation of 

 anaphylatoxin. It may be permitted to illustrate this with a protocol 

 of one of the writer's experiments with typhoid bacilli, since, though 

 merely confirming the principle laid down by Friedberger, it in- 

 cluded a careful titration of the bactericidal contents of the anti- 

 typhoid serum. (See table on p. 417.) 



Two-tenths c. c. of this serum added to 1 c. c. of typhoid filtrate 

 gave a very slight clouding in about 15 minutes. 



ANAPHYLATOXIN EXPERIMENTS 



The weak character of the antiserum used, and the fact that, 

 in this experiment, the digestion was at to 5 C., explain the 

 failure to obtain a strong anaphylatoxin with 1 c. c. of sensitizing 

 serum. 



The negative experiment resulting from a too vigorous sensi- 

 tization is practically a corollary of the next point ascertained by 

 Friedberger, namely, that : 



3. With constant amounts of reagents a too prolonged exposure 

 at 37 C. will result in failure to obtain the poison. 



How are we to explain these experimental results ? The first of 

 the three namely, the fact that an excess of bacteria inhibits the 

 formation of anaphylatoxins seems to the writer most easily ex- 

 plained by accepting the views of Bordet on the manner of the 

 union of an antigen with its antibody. For, unlike the opinion of 

 Ehrlich, who assumes a union of the two according to the laws of 

 multiple proportions, Bordet 21 believes that the distribution of 

 serum substances upon an antigen is such that the entire amount of 

 antibody is distributed equally among the antigenic elements. In 

 the case of an excess of bacteria, as in these experiments,' therefore, 

 the quantity falling to each unit is insufficient, at least in the time of 

 exposure here practised, to accomplish the cleavage necessary for 

 poison production. 



21 Bordet. Ann. de I'Inst. Past., 17, p. 161, 1903. 



