The work recorded above has served to corroborate the observations of other writers, notably of Noguchi, that in many human sera, if not in all, there develop, on standing, anticomplementary bodies which are delicately thermolabile, being inactivated by heating to 56° C. for fifteen to twenty minutes. It has appeared that these bodies may occasionally be present in sera which, after heating, may develop the thermostable anticomplementary body referred to by other authors. It has become evident also that the speed of development of the thermolabile anticomplementary body in different sera is subject to much variation. The thermolabile body appears as the complement disappears. The question arises whether the thermolabile anticomplementary body may not be originally present in the serum, temporarily masked by the native complement. This would seem improbable from the fact that titration has shown that 0.1 and 0.2 cubic centimeter of the inhibiting serum will often inhibit as much as 0.6 cubic centimeter of fresh guinea-pig complement, a quantity superior to the amount of complement present originally in the antihemolytic serum. It seems, therefore, that the anticomplementary body must actually be formed in the serum during the period of preservation.

The thermolabile antihemolytic body studied by us is like the thermostabile body investigated by Noguchi, in that it inhibits alien as well as homologous complement; it is unlike the thermostabile body, however, in that it cannot be absorbed from serum by digestion with red cells, nor does it render the treated cells more resistant to hemolysis.

The thermolabile body may be removed from inhibiting sera by precipitating the globulins. A solution of the glotmiins then manifests a thermolabile anticomplementary action.

No relationship between a clinical condition and the appearance of these bodies in the sera, has been found.

As a practical result these studies have shown, as have those of Noguchi, that the complement fixation tests should never be made with certain sera which have been preserved for some time without inactivation.

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