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The addition of latex particles to native (no anticoagulant) or citratcd human platclctrich plasma (PRP), or to a once-washed platelct suspension causes platelet aggregation. This aggregation is associated with phagocytosis of t'ae latex particles by the platelets and appcars to be due to release of adenosine diphosphate (ADP) from the platclets. Adenosinc and adenosine monophosphate, which are known to inhibit platelet aggregation induced by ADP, also block that induced by latex. These compounds do not prevent the phagocytosis of latex particles by the platelet. The addition of iodoacctate and 2,4-dinitrophcnol in appropriate concentrations to the PRP, prior to the addition of the latex, blocks platelet aggregation and phagocytosis. This is also true for the chelating agent ethylenediaminetetraacetate (EDTA). Platclets left in contact with latex for a sufficient period of time show loss of their granules. Leucocytcs phagocytose both latex and platelets that had themselves phagocytosed latex. It is concluded that phagocytosis of latex particlcs by platelcts rcscmblcs that by white cells, and that in both processes metabolic changes appear to bc involved.

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TABLE 11. Reactivity of Human Hemoglobin After Chemical Treatment. Ratio of reactivity with 'Treatment human serum* (%) Hemoglobin + .02 M NaCN + .2 M potassium ferricyanide0 " + .5 M potassium f erricyanide 77.5 " + . 5 M N a C N 10.0 " + .5 M sodium azide 100 " + .1 M 8-mercaptoethanol 100 " (2.0 cc) + carbon monoxide (5,OO cc, research grade, room 1010 " + .15 M NaCl (control) 100 temp I% pressure) tAdult hernoglobin, 25 mg/ml, (95% Hgb A) was used. Samples were reacted at room temperature for one hour, then dialyzed against 3 changes of 0.15 M NaC1, 18 hr at 4°C before testing. Tests were made i n " buffered agar ) ' containing 0.5 mg/ml of the treated hemoglobin, incubated 20 hr, 23-24°C.* Ratio, in %, of precipitate ring sizes formed by several concentrations of human Serum in agar containing each hemoglobin sample relative t o ring sizes formed by the same concentratiom of this serum with agar containing the control hemoglobin.t This sample was not dialyzed before testing.Thus far the precipitate reaction between albumin and hemoglobin has been noted only in agar medium, and several attempts to demonstrate it in liquid medium, or in gelatin gels have failed ( 6,12 ) .Summary. Human serum albumin precipitates in agar gels with hemoglobin. This reaction can be quantified by means of a diffusion ring test, described, and is maximal between pH 6 and 8 when the medium contains 0.01 to 0.1 M NaCl. Several human and ani-ma1 hemoglobins display varying reactivities. Conversion of hemoglobin to cyanmethemoglobin abolishes reactivity. It is suggested that the specificity of the reaction depends on both the globin and heme moieties of hemoglobin. ~~ ~ ~~~ ~-1. Polonovski, M., Jayle, M.